A. GENERAL STATEMENT OF THE CLASS SUBJECT MATTER
1. This class includes electric wave transmission systems wherein electromagnetic wave energy is guided or constrained by a wave transmission device of the long line type other than loaded lines.
2. Included are passive wave transmission networks simulating the characteristics of a long line wave transmission systems or wave guides, such as artificial lines, delay networks, resonators, impedance matching networks, equalizers, wave filters and transmission line terminations.
3. Also included are passive coupling networks and terminating networks having either lumped or distributed electrical circuit parameters and having impedance characteristics peculiarly adapted for use with the wave transmission systems of paragraph 1, above, or which are designed to be frequency responsive, or which are designed to be effective over or within a range of frequencies, for example, impedance matching networks, hybrid networks, coupling networks, wave shaping networks, phase shifting networks, wave filters, equalizers and attenuators.
4. Smoothing type wave filters having shunt capacitance, or series inductance, or both, usually designed to pass direct current and to reduce the effect of any undesired alternating or pulsating current superimposed on the direct current, or to pass direct current and low frequency alternating current or pulsating current and to reduce the effect of an undesired higher frequency alternating or pulsating current.
5. Networks including a wave transmission device and means for decreasing the amplitude range of the signal applied to the transmission device as the signal increases in amplitude and means for increasing or restoring the amplitude range of the signal after the transmission over the transmission device (i.e., companders).
6. Passive networks for producing an output wave which is the time derivative or time integral of the input wave (i.e., differentiating or integrating systems).
7. Systems including active elements for producing across at least two of the system terminals a negative resistance, and/or an inductance, or capacitance which may be positive or negative.
8. Wave traps using long line elements.
9. Transmission systems including only one or more of the systems or networks defined in paragraphs 1 - 8, above, and such systems in combination with current or voltage magnitude control means of the passive type. Systems including two or more of the networks or systems defined in paragraphs 1 - 8, above, are classified as set forth in the Class Definition, subsection C, below.
10. Components and elements not constituting a complete system or network limited by claimed structure to use in the systems or network of paragraph 1, above, and not otherwise classified, and also long line elements.
B. ACTIVE NETWORK
The systems classified in this class ordinarily contain no active elements, the only exceptions being the amplitude compression and expansion systems (companders) and negative resistance and/or reactance networks of the active element type found in this class. See Subclass References to the Current Class, below.

LINES WITH OTHER CLASSES AND WITHIN THIS CLASS
SYSTEM AND NETWORKS INCLUDING TWO OR MORE OF THE NETWORKS AS DEFINED IN 1 - 8 OF THE CLASS DEFINITION
Such systems and networks which include two or more of the networks or systems so that each has its own function, and one is not merely part of the other, are classified in the first occurring subclass and cross-referenced to the later occurring subclass or subclasses. For instance, a filter (subclasses 167+) combined with a wave shaper (subclass 20) is classified in subclass 20 and cross-referenced to subclasses 167+. Where the combinations of the plural networks are useful as a third device having its own function provided for in the schedule, the patent is classified in the subclass providing for the third device. For example, the combination of a resonator (subclasses 219+) and a long line (subclasses 236+) which results in an interference elimination device (subclass 12) would be classified in subclass 12 and cross-referenced to subclasses 219+ and 236+ for novel resonator or long line structure if necessary. Where one of the networks is only a part of another network, the patent is classified on the basis of the combination and cross-referenced if necessary for the part. For example, a filter (subclasses 167+) including a long line element with impedance matching (subclass 32) where the over-all function of the network is filtering and not impedance matching, is classified in subclasses 202+ and cross-referenced to
subclasses 33+ if necessary.
NETWORKS AND SYSTEMS WITH SPECIFIC SOURCE OF INPUT ENERGY
This class does not provide for the subject matter of the class (Class Definition paragraphs 1-10 above) in combination with a specific source of electromagnetic wave energy, such as a microphone, which limits the system to use with a particular art even though the source is recited by name only. However, this class will take the systems and networks of the class in combination with a source of wave energy which is recited by its characteristics; for example, as being composed of a band of frequencies with only odd harmonics, or where the source is recited only as a general class of wave energy generators, such as an oscillator, etc., where the specific characteristics and details of the source are recited, such as specific oscillator system details, the system or network is classified with the specific source.
NETWORKS AND SYSTEMS WITH SPECIFIC LOADS IN THE OUTPUT CIRCUIT
This class does not provide for the subject matter of the class (Class Definition, paragraphs 1 to 10 above) in combination with a specific load device supplied with energy by the system or network, even though the load device is recited by name only (as a motor, loudspeaker, piezoelectric crystal, etc.). Such systems and networks are classified with the art which provides for the systems of supply for the specific load device.
SYSTEMS AND NETWORKS AND COMPONENTS IN OTHER CLASSES GENERIC TO THE SUBJECT MATTER OF THIS CLASS
See References to Other Classes below.
WAVE TRANSMISSION LINE AND NET WORKS ANALOGOUS TO THOSE IN THIS CLASS, BUT WHICH ARE CLASSIFIED ELSEWHERE
See References to Other Classes.
TESTING AND MEASURING SYSTEMS FOR WAVE TRANSMISSION LINES AND NETWORKS
This class (333) will take systems for determining the electrical wave propagation characteristics of transmission lines and networks falling within the class definition, provided that significant details of the transmission line or network are claimed. That is, merely claiming the line or network by name only (e.g., as a transmission line, coupling network or resonator) or characterizing it as a four terminal or two terminal impedance network would not be sufficient basis for classification in this class, classification would then be in one of the classes indicated below, depending on the nature of the test or measurement.
1. Long Telephone Lines:
Systems and apparatus for testing long telephone lines to determine impedance irregularities, unbalance in loaded lines, impedance versus frequency characteristics, impedance versus delay characteristics, or other long telephone line characteristics are classified elsewhere. See References to Other Classes, below
2. Power, Voltage and/or Current Determination in Wave Transmission Lines or Networks:
Apparatus for measuring the voltage or current, or the voltage or current standing wave ratio, or power dissipation in wave transmission lines are classified in elsewhere. See References to Other Classes, below
3. Impedance Characteristic of Networks or Network Elements:
Systems for determining the inductance, capacitance or resistance, or any of these properties over a range of frequencies, of four-terminal or two-terminal impedance networks in general are classified in elsewhere. See References to Other Classes, below
4. Wave Frequency Determination Systems:
Wave frequency determination systems having means giving a direct quantitative indication of the frequency of electrical currents are classified elsewhere. See References to Other Classes, below.
Frequency meters which measure frequency by utilizing phase shift networks are classified elsewhere. See References to Other Classes.
5. Wave Meters:
Wave Meters for determining the wave length of electrical waves are classified elsewhere.
6. Electromagnetic Radiation Field Strength Measurement:
Apparatus for measuring electromagnetic radiation field strength is classified elsewhere. See References to Other Classes.
7. Wave Analyzing Systems:
Devices for determining the individual frequency components of a complex electric wave, and such devices which also determine the amplitude or relative phase positions of the different frequency components of the complex wave are classified elsewhere. See References to Other Classes.
Speech wave analyzing devices are classified elsewhere. See References to Other Classes.
CONDUCTOR STRUCTURE, ARRANGEMENTS AND COMPONENTS
See References to Other Classes below..
SYSTEMS UTILIZING WAVE TRANSMISSION LINES AND NETWORKS
See References to Other Classes.

SEE OR SEARCH THIS CLASS, SUBCLASS:
1 for plural channel systems wherein passive means, such as wave filters, are employed to separate plural messages or signals.
14 for amplitude compression and expansion systems (companders).
213 for negative resistance and/or reactance networks of the active element type.

REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:
84, Music, subclass 661, 699 or 736 for electrical tone generating and music instruments with electric translating devices including coupling networks or wave filters. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks)
138, Pipes and Tubular Conduits, appropriate subclasses for conduits (including wave guides) and conduit and pipe accessories disclosed for electrical use even though the conduit is made of or lined with metal or insulating material unless there is claimed some structure or feature which limits the same to electrical use in addition to mere pipe or conduit structure. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
138, Pipes and Tubular Conduits, provides for conduit and pipe structure and accessories. See Lines With Other Classes, "Systems and Networks and Components in Other Classes, Generic to the Subject Matter of This Class (and related class references) above. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
174, Electricity: Conductors and Insulators, appropriate subclasses for housings, conductor and conduit structure and for conductor and conduit joint and end structure which include electrical features and which are not defined as having long line characteristics, and 137 for insulator structures. See subclasses 32+ for conductor arrangements and structures for preventing or reducing the detrimental effects due to either the self-inductance of a single conductor or mutual inductance between plural conductors, subclasses 27
and 113+ for parallel or twisted conductor structure, subclasses 28+ and 102+ for coaxial and shielded cable structure, subclasses 37+ for underground conductor structure, subclasses 38, 43, 49, and 71+ for branched electrical conductor structure, and subclasses 40+ for overhead conductor structure. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
174, Electricity: Conductors and Insulators, provides for conductor structure, insulator structure and transmission accessories (e.g., boxes, shields, housing). (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
178, Telegraphy, subclass 45 provides for loaded lines and all systems and networks analogous to the systems or networks in this class (333) which include loaded lines. Subclasses 69+ includes patents relating to line clearing, circuit maintenance and anti-inductive lines analogous to similar systems in subclass 12 of Class 333. (See Lines With Other Classes, "Wave Transmission Line and Net Works Analogous to Those in This Class, etc.")
178, Telegraphy, subclass 46 provides for loading coils for use with loaded lines. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
178, Telegraphy, for telegraph systems utilizing wave transmission lines and networks, especially subclass 43, for space induction radiation systems, subclasses 45+ for loaded transmission line systems; subclass 49 for systems wherein currents (signaling or otherwise) and telegraph signal currents are superposed on the same transmission path, subclass 63 for cable systems including means for correcting for telegraph signal distortion caused by cable capacitance; subclass 64 for wave transmission line systems including mutual induction type coupling networks or transformers; subclasses 66.1+ for alternating current systems, other than harmonic or vibrating reed systems (for which see subclass 47); subclasses 66.1+ for pulsating current systems; and subclass 69 for telegraph systems wherein wave transmission networks are utilized to correct for the deleterious effects of line charges and surges which may cause signal distortion. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
191, Electricity: Transmission to Vehicles, 2 for electrical transmission line systems and coupling means for transmitting electric current between relatively movable source and load and subclass 10 for systems wherein the transmission of energy between the relatively movable source and load is effected through an induction field coupling means. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
200, Electricity: Circuit Makers and Breakers, appropriate
subclasses for electric switches of general utility and not limited by claimed structure to use with long lines. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
200, Electricity: Circuit Makers and Breakers, provides for electric switches (See Lines With Other Classes, "Systems and Networks and Components in Other Classes, Generic to the Subject Matter of This Class (and related class references) above). (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
219, Electric Heating, wherein wave transmission lines or coupling networks are employed in electrical heating systems. Note 600 for inductive heating, subclasses 678+ for microwave heating, and subclasses 764+ for capacitive dielectric heating, subclasses 50+, especially subclasses 108+ and 130.1+ for metal heating systems, and subclasses 482+ for electrical heating systems in general. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
246, Railway Switches and Signals, for wave transmission networks that may be employed in railway electric signaling and control, especially 7 for train telegraphy and telephony used for train dispatching, subclass 30 for automatic block signal systems controlled by hertzian waves, subclass 61 for automatic block signal systems wherein the signal and propulsion currents are superimposed, subclass 63 for cab signal or train control systems wherein signals or control currents are transferred between the train and the transmission line by induction and subclasses 72, 81+ for systems wherein the signaling energy is derived from the propulsion current. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
250, Radiant Energy, subclass 250 and in Class 324, Electricity: Measuring and Testing, subclasses 76.39+, especially subclasses 76.41+ and 76.51, for determining the wave length of electrical waves.
257, Active Solid-State Devices (e.g., Transistors, Solid-State Diodes), subclasses 661-664. (See Lines With Other Classes, "Conductor Structure and Within This Class, Arrangements and Components")
307, Electrical Transmission or Interconnection Systems, for miscellaneous transmission or interconnection systems not otherwise classified. For example, Class 307 provides for subject matter similar to that classified in Class 323 where there are plural input circuits and/or plural output circuits. Class 307 also provides for some systems which include one or more long line elements where the system includes an active element so that the system is excluded from Class 333. See the pulse forming and wave shaping in 106 for example. Class 307 is also the miscellaneous class
for anti-inductive systems (see subclasses 89+). (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
307, Electrical Transmission or Interconnection Systems, 147 is the miscellaneous subclass for conductor arrangements or structure. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes, Generic to the Subject Matter of This Class (and related class references) above). (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
307, Electrical Transmission or Interconnection Systems, is the generic place for electrical energy distributing and/or controlling and/or generating systems for which provision is not made in any other electrical system class. By way of example, provision is made for 1 for systems with superimposed unlike currents, subclasses 11+ for plural load systems, subclasses 43+ for plural supply circuits or sources, subclasses 401+ for semiconductor (i.e., transistor) electric or transductor system, subclasses 89+ for anti-induction or coupling to other systems, subclasses 326+ for self protective, safety or limit control systems, subclasses 98+ for combined impedance and switch systems, subclass 103 for line drop compensation, subclass 104 for electromagnet or highly inductive systems, subclass 105 for harmonic filtering or neutralizing systems, subclasses 106+ for wave form, wave shaping or pulse producing systems, subclasses 112+ for switching systems, subclasses 147+ for conductor arrangements or structure, and subclasses 149+ for miscellaneous systems. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
315, Electric Lamp and Discharge Devices: Systems, particularly 4 for cathode-ray tubes having long line elements or resonators structurally combined therewith, subclass 39 for a space discharge device structurally combined with wave guide, coaxial cable or resonant parallel wire transmission line, and subclass 40 for space discharge devices with an electrode formed as an inductive impedance (e.g., magnetron). (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
323, Electricity: Power Supply or Regulation Systems, provides for miscellaneous transformer systems in subclass 355 and for miscellaneous impedance systems in subclass 364, where the system or network has only a single input and a single output. Class 323 also provides for the miscellaneous systems for controlling the magnitude of the current and/or the voltage and/or for controlling the phase in systems and networks having only a single input and a single output circuit where the same current is in the output as is in the input. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
323, Electricity: Power Supply or Regulation Systems,
subclass 355 provides for the miscellaneous structural arrangement of a transformer and other electrical devices which are connected together, and subclass 364 provides for the miscellaneous structural arrangements of impedance elements, which are connected together to form a network. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
324, Electricity: Measuring and Testing, for electrical testing systems utilizing wave transmission networks or for measuring impedance characteristics of electrical networks in general, subclass 72, 95, 140+, and 612+ for electric power, current and/or voltage measuring systems for systems employing wave transmission lines or networks for determining reflected power or standing wave amplitude ratios and subclasses 76.77+ for electric phase angle measuring systems including electric wave transmission lines or networks used for time delay or coupling purposes. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
324, Electricity: Measuring and Testing, 600 for Systems for determining the inductance, capacitance or resistance, or any of these properties over a range of frequencies, of four-terminal or two-terminal impedance networks in general; subclasses 76.77+ for phase shift or phase relations between voltages or currents or voltage and current in electrical systems in general.
324, Electricity: Measuring and Testing, 76.12 and 76.39+ for means giving a direct quantitative indication of the frequency of electrical currents.
324, Electricity: Measuring and Testing, 76.52 for frequency meters which measure frequency by utilizing phase shift networks.
324, Electricity: Measuring and Testing, 76.11, for apparatus for measuring electromagnetic radiation field strength.
324, Electricity: Measuring and Testing, 76.12, for devices for determining the individual frequency components of a complex electric wave, and such devices which also determine the amplitude or relative phase positions of the different frequency components of the complex wave.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for miscellaneous nonlinear circuits which may utilize an active device such as a transistor or electron tube. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, appropriate subclasses for miscellaneous circuits which may incorporate a transmission
line device. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
329, Demodulators, subclass 322 and 354+ for a demodulator with distributed electrical parameters. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
330, Amplifiers, appropriate subclasses, for one way amplifiers utilizing wave transmission networks or filters for input, output, or interstage coupling, particularly 53, 116, 117, 120+, 122, 157+, 185+, and 192+. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
331, Oscillators, for oscillation generators utilizing wave transmission lines and networks as elements thereof, particularly subclass 5, 6+, 9, 79+, 86+, 93, and 96+ for oscillator systems employing distributed parameter networks or resonators, subclasses 110 and 138+ for oscillators employing bridge networks, subclasses 86+, 115, 126+, and 132+ for oscillators of the negative resistance type, subclass 135+ for oscillators employing phase shift networks, subclasses 74+ for oscillators combined with a particular output coupling network and subclasses 73, 116, 139, and 154+ for oscillators employing an electromechanical resonator. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
332, Modulators, for modulation systems utilizing wave coupling networks, long line sections or negative impedance devices as elements thereof, particularly 129 and 138+ under frequency modulators and subclasses 163+, 175 and 176+ under amplitude modulators. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
334, Tuners, provides for tuners which are closely analogous to the wave filters in this class. The tuners usually have inductance and capacitance elements of the lumped type together with means to vary either the inductance or capacitance element or both in order to change the mean resonant frequency of the tuner. The tuners in Class 334 may include one or more long line elements in addition to a lumped inductor or capacitor; or the tuner may consist of a distributed parameter type tuning unit which is adjusted in discrete, distinct steps; or where two or more distributed parameter type tuning units are ganged together either mechanically and/or electrically so as to have their mean resonant frequency adjusted in unison. Where only the band width of a filter is varied without varying the mean resonant frequency, classification is in this class (333). (See Lines With Other Classes, "Wave Transmission Line and Networks Analogous to Those in This Class, etc.", "Systems and Networks and Components in Other Classes, Generic to the Subject Matter of This Class"; "Conductor Structure, Arrangements and Components")
334, Tuners, appropriate subclasses for tuned networks for use in wave energy apparatus and comprising inductance and capacitance elements in circuit arrangement to form a resonant circuit and in which structure is provided for adjusting one or both of these elements for changing the mean resonant frequency of the circuit. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
336, Inductor Devices, appropriate subclasses for transformers and inductors which are not designed to be frequency responsive (e.g., not having points of resonance within the range of frequencies over which the device is designed to operate). (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class; and "Conductor Structure, Arrangements and Components")
338, Electrical Resistors, appropriate subclasses, for fixed and variable electric resistors, per se. See (2) Note under Class 333, subclass 22, for the distinction between the resistors in Class 338 and the dissipating terminals for long lines. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class)
338, Electrical Resistors, provides for fixed and variable resistors. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes, Generic to the Subject Matter of This Class (and related class references) above). (See Lines With Other Classes, "Conductor Structure, Arrangements and Components)
340, Communications: Electrical, for electrical communication systems in general having wave transmission lines and networks as elements thereof, particularly 825.37 for party line type selective systems, subclasses 825.57+ for pulse responsive selective systems, subclass 825.70 for phase responsive selective systems, subclasses 825.71+ for frequency responsive selective systems, subclasses 825.77+ for amplitude responsive systems, subclasses 870.01+ continuously variable indication systems (e.g., telemetering), subclasses 286+ for miscellaneous signaling systems, and subclasses 310.01+ for composite signaling systems (e.g., signal over power line).
343, Communications: Radio Wave, for radio wave energy systems which employ wave transmission lines and networks as elements thereof, 5 for reflected or returned wave systems, (e.g., object detection radar), subclasses 350+ for directive systems (including polarization), subclasses 700+ for antennas involving wave transmission lines and networks including long line sections, usually resonant, designed to act as space radiators or collectors of electromagnetic waves. See (11) Note under subclass 700 of Class 343 for classification lines between coupling networks and antennas with such coupling networks. (See Lines With Other Classes,
"Systems Utilizing Wave Transmission Lines and Networks")
360, Dynamic Magnetic Information Storage or Retrieval, for magnetic recorders or reproducers having wave transmission networks as elements thereof. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
361, Electricity: Electrical Systems and Devices, 271 for capacitors, subclasses 600+ for miscellaneous arrangements for mounting two or more different circuit elements which are not in circuit arrangement (including printed circuits), and subclasses 503+ for electrolytic capacitors. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
361, Electricity: Electrical Systems and Devices, 107 for wave transmission networks for use in surge suppression circuits, and subclasses 117+ for lightning arresters. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
363, Electric Power Conversion Systems, particularly 2, 9+ and 36 for phase conversion systems (e.g., m-phase to n-phase) combined with other types of conversion, subclasses 39+ for current conversion systems combined with means to eliminate undesired frequency components (e.g., filter), and subclasses 148+ for phase conversion systems, per se. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
364, Electrical Computers and Data Processing Systems, appropriate subclasses, (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks)
365, Static Information Storage and Retrieval, appropriate subclass for read/write static storage systems, particularly subclass 194, 198, and 223 which include delay, transmission, and bridge means for a read/write circuit. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
367, Communication, Electrical: Acoustic Wave Systems and Devices, 197 for selective systems which are sound responsive. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
370, Multiplex Communications, appropriate subclasses for multiplexing systems, particularly subclass 272 for a sextuplex system, subclasses 273+ for a quadruplex system, subclasses 276+ for a duplex system, and subclass 297 for a diplex system. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
379, Telephonic Communications, 22 for systems and apparatus for testing long telephone lines to determine impedance irregularities, unbalance in loaded lines, impedance versus frequency characteristics, impedance versus delay
characteristics, or other long telephone line characteristics.
379, Telephonic Communications, subclass 398 includes loaded line systems and anti-inductive systems analogous to the subject matter of this class (333). (See Lines With Other Classes, "Wave Transmission Line and Net Works Analogous to Those in This Class, etc.")
379, Telephonic Communications, 443 provides for telephone induction coils. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
379, Telephony, appropriate subclasses, especially 90 for composite systems, employing wave transmission networks wherein voice signal systems are combined with other electrical systems, such as telegraph, power or lighting systems (Note that this class (333) provides for plural channel systems wherein passive means, such as wave filters, are employed to separate plural messages or signals. (See Subclass References to the Current Class, above)); subclass 78 for wave transmission networks used to compensate for or prevent detrimental effects on telephone systems of internal or external induction or radiation fields; subclass 79 for such systems under subclass 78, utilizing capacitive reactance for compensation and subclass 80, under subclass 78, wherein the compensation means comprises impedance coils; subclass 81, for telephone substation circuits employing wave coupling networks of the conjugate or Whetstone bridge type and/or balancing networks; subclass 82 for space induction radiation systems having wave transmission networks as elements thereof, subclasses 170+ for telephone repeaters (i.e., two-way amplifiers) utilizing hybrid networks and line balancing networks; subclasses 172+ for coupling devices of the induction coil type associated with telephone instruments; subclass 174 for anti-induction devices including wave transmission networks for preventing the undesirable effects of induction in telephone systems or instruments, other than those anti-induction devices in subscribers circuits, for which see subclasses 78+, 81; and subclass 175 for testing devices utilizing wave transmission networks for telephone systems or devices, not particularly subclasses 175.3+ under subclass 175 for testing long telephone lines and associated apparatus.
439, Electrical Connectors, provides for miscellaneous connector structure (see 55 for preformed or printed circuit arrangements involving only conductors and connector structure). (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
455, Telecommunications, appropriate subclasses for filters analogous to those in this class and forming an element of radio communication systems. (See Lines With Other Classes, "Wave Transmission Line and Net Works Analogous to Those in This Class, etc.")
455, Telecommunications, 334 for miscellaneous circuitry and apparatus which are specialized to use with radio apparatus. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
455, Telecommunications, 39 provide for modulated carrier wave systems of general application; subclasses 91+ provide for transmitters employing wave transmission lines, wave guides and networks for coupling the transmitter to an antenna; subclasses 130+ for radio receiver coupling and selecting networks, see particularly subclasses 132+, 3.1+ and 272+ for plural channel systems; subclasses 280+ for means for coupling antennas to radio receivers; subclasses 150+ for frequency selection networks; subclass 307 for filter means for noise elimination; and subclasses 338+ for miscellaneous coupling means. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Networks")
505, Superconductor Technology: Apparatus, Material, Process, 150 for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting devices, and particularly subclasses 210+ for transmission line and networks, electrical energy storage devices, magnetic coils, wires, cable, etc. (See Lines With Other Classes, "Systems and Networks and Components in Other Classes Generic to the Subject Matter of This Class")
505, Superconductor Technology: Apparatus, Material, Process, 150 for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting devices, and particularly subclasses 210+ for transmission line and networks, electrical energy storage devices, magnetic coils, wires, cable, etc. (See Lines With Other Classes, "Wave Transmission Line and Net Works Analogous to Those in This Class, but Which Are Classified Elsewhere")
505, Superconductor Technology: Apparatus, Material, Process, 150 for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting devices, and particularly subclasses 210+ for transmission line and networks, electrical energy storage devices, magnetic coils, wires, cable, etc. (See Lines With Other Classes, "Conductor Structure, Arrangements and Components")
505, Superconductor Technology: Apparatus, Material, Process, 150 for high temperature (T[subscrpt]c[end subscrpt] 30 K) superconducting devices, and particularly subclasses 210+ for transmission line and networks, electrical energy storage devices, magnetic coils, wires, cable, etc. (See Lines With Other Classes, "Systems Utilizing Wave Transmission Lines and Network"s)
703, Data Processing: Structural Design, Modeling, Simulation, and Emulation, subclasses 13-22 for the simulation of electronic device or electrical system.
704, Data Processing: Speech Signal Processing, Linguistics,
Language Translation, and Audio Compression/Decompression, 200, for speech wave analyzing devices.
708, Electrical Computers: Arithmetic Processing and Calculating, subclass 818 for correlation or convolution with tapped delay line, and subclass 819 for electrical analog filtering devices.

GLOSSARY:
ACTIVE NETWORK
A network containing a source of energy, or a sink of energy (i.e., a device for absorbing or dissipating energy other than that accounted for by the resistance of the components of the networks). Merely dissipating the heat generated by a resistance will not cause the resistance to be an active element.
AMPLITUDE RANGE
The ratio of the highest amplitude to the lowest amplitude of an undulating wave.
AMPLITUDE RANGE COMPRESSOR
A nonlinear device having an input and an output, the amplitude range of the output wave being less than the amplitude range of the input wave.
AMPLITUDE RANGE EXPANDER
A nonlinear device having an input and an output, the amplitude range of the output wave being larger than the amplitude range of the input wave.
ARTIFICIAL LINES
Networks for simulating impedance characteristics of a smooth or loaded electrically long transmission line over a frequency range.
ATTENUATOR
Devices and networks consisting of one or more elements which exhibit only a positive resistance effect and which reduce the intensity of the energy passing through the device by dissipation, (a) the elements being proportioned to permit a change in their value to control the energy loss while maintaining substantially constant input and/or output impedance of the device, and/or (b) the elements being proportioned to permit the device to be inserted in the circuit to provide an energy loss without introducing any reflections in the circuit, and/or (c) the elements being combined with a long line or long line element, and/or (d) the device or network having an impedance equal to the impedance of a specified long line, and/or (e) the device or
network is claimed as being particularly modified for use over a frequency band so that its characteristics are particularly related to frequency.
BALANCED CIRCUIT
A circuit having its conductors electrically symmetrical with respect to a reference potential plane (e.g., ground). The potentials between the two sides and ground are equal and of opposite sign. For example, a horizontal two wire line may be a balanced line.
CHARACTERISTIC IMPEDANCE
The impedance which a long line or a long line element would have if it were infinitely long. A long line which is terminated in its characteristic impedance is not resonant.
COMPANDER
An amplitude range compressor connected to an amplitude range expander with or without an intervening transmission line so that the amplitude range of the input wave is first decreased in the compressor and then increased in the expander.
COUPLING NETWORKS
(a) Networks including significant reactive structure for effecting the transfer of oscillatory energy from one circuit to another circuit and having attenuation and/or delay characteristics over a frequency range for attenuating and/or delaying in a predetermined manner wave energy passing therethrough, and/or providing an impedance match between the network and at least one of the circuits; (b) smoothing type wave filters having shunt capacitance, or series inductance, or both usually designed to pass direct current and to reduce the effect of any undesired alternating or pulsating current, or to pass direct current and low frequency alternating current or pulsating current and to reduce the effect of any undesired higher frequency alternating or pulsating current.
DELAY
Includes phase distortion and also includes the retardation of a single pulse with respect to time.
DELAY NETWORK
Networks including significant structure for retarding wave energy a predetermined period of time over a range of frequencies.
DISSIPATING TERMINATIONS: (FOR LONG LINES)
Networks specialized for use with and designed for connection to the end of a long line transmission line and including a resistive component for dissipating the wave energy
propagated along the line and presenting an essentially resistive impedance to the line.
DISTRIBUTED PARAMETERS
When the impedance of a transmission device or line at the operating frequency or band of frequencies is due primarily to the parameters of the device or line itself, and in considering the inductance, capacitance and resistance of the device or line they must be considered as mixed together and spread out along the device or line rather than being considered as in separate discrete lumps or devices as in the case of simple series and parallel circuits, the transmission device or line ay be said to have distributed parameters. Examples of circuits with distributed parameters include telephone, telegraph and power lines for high frequency energy.
EQUALIZER
Networks with attenuation or attenuation and phase distortion characteristics which vary over a frequency range for use in a wave transmission system for modifying the attenuation or attenuation and phase characteristics of the wave energy as a function of frequency.
FREQUENCY RESPONSIVE NETWORK
As the frequency of the applied energy changes over a band, the impedance of the network varies as a function of the frequency. Frequency responsive networks and devices are designed to obtain desired characteristics where a band of frequencies or different frequencies are involved.
HYBRID TYPE NETWORK
A network for coupling one wave transmission line to two or more wave transmission lines in such manner that there is a conjugate relation between at least two of these coupled transmission lines to prevent any interchange of energy between the conjugately related lines.
IMPEDANCE MATCHING NETWORK
Coupling networks which include one or more impedance elements construed or proportioned to substantially eliminate the reflected wave energy between the network and at least one of the connected circuits caused by impedance differences.
LOADED LINES
A long line to which lumped impedance elements, usually capacitors or inductors, are added at regularly spaced points along the length thereof, or to which an added impedance is applied in a continuous manner, as for example, by wrapping a strip of magnetic material about the line or device to
increase the inductance of the line or device.
LONG LINE
A wave transmission device or line having distributed parameters and especially designed to propagate electrical wave energy where the wave length of the transmitted energy is relatively short when compared with the length of the transmission line or device. The impedance of a long line is practically fixed by the constants of the line itself. The length of the transmission line or device may be a multiple or a fraction of a wave length, e.g., 1/4, 1/2, etc., or otherwise have its length proportioned to the wave length of the energy with which it is to be used.
LONG LINE ELEMENT
A circuit element having distributed parameters, such as a resonator, or a wave guide. A long line element may be a part of a long line wave transmission device or used in a network with other circuit elements of the lumped parameter type, for example, as in the case of delay networks, impedance matching networks, wave filters.
LUMPED PARAMETERS OR IMPEDANCES
When the impedance of a transmission line or device at the operating frequency may be considered as equivalent to devices concentrated at one point, and the parameters of the system including the line or device is not substantially independent of the load devices connected thereto, the transmission line or device may be said to have lumped parameters. Lumped impedances is also used to include devices such as capacitors, inductors, and resistors which have their impedance concentrated at the terminals thereof.
NETWORK
A network is made up of two or more resistances, inductances, capacities or mutual inductances connected together in some manner.
PASSIVE NETWORK
A network containing no source of energy and in which no energy is dissipated other than that accounted for the resistance of the components of the network.
PHASE DISTORTION
Results from different frequencies travelling with different velocities such that their relative arrival times differ from their relative starting times.
PHASE DISTORTION CHARACTERISTIC
Used to designate the change in displacement of different
frequency components of a band of frequencies transmitted by a transmission device or network. For example, certain frequencies of the band will be retarded or advanced a different amount than other frequencies.
PHASE SHIFT
Used to designate the change in phase relation between voltage and current of the same wave energy, or between the voltages or the currents of different wave energy of the same frequency.
RESONATOR
Devices comprising conductive enclosures, cavities, or wave transmission line sections of the two terminal type, and having distributed inductance and capacitance, the line sections being terminated in other than the characteristic impedance of the line sections, the devices presenting resonant characteristics to the existing source of wave energy.
TAPERED LONG LINE
A long line having a physical dimension which changes progressively in the direction of wave propagation along the line.
TRANSMISSION LINE
As used in the subclass definitions is synonymous with wave transmission devices.
UNBALANCED CIRCUIT
A circuit having its conductors electrically unsymmetrical with reference to a potential plane. For example, a concentric line is ordinarily unbalanced, the outer conductor being ordinarily connected to ground.
WAVE ENERGY
An undulatory disturbance propagated through a medium, (usually periodic in nature), its displacement varying periodically with respect to time or distance or both. The wave may be manifested in electrical, mechanical or acoustical form. However, in this class the term "wave energy" refers only to electrical wave energy.
WAVE FILTER
Coupling networks which include significant structure permitting free transmission of electric waves of a single frequency or band of frequencies (which may include zero frequency) while attenuating substantially electric waves having other frequencies, or attenuating substantially electric waves of a single frequency or band of frequencies
(which may include zero frequency) while permitting free transmission of electric waves having other frequencies.
WAVE GUIDE
A transmission device designed to propagate electrical waves having an electric or magnetic field component extending in the direction of propagation. The wave guide may be a hollow dielectric or metal tube, or a solid dielectric rod, the wave energy being propagated along the interior of the tube or rod and confined by the walls of the tube or rod.
WAVE PROPAGATION CHARACTERISTIC
Effect of the impedance characteristic of the transmission device upon the wave energy propagated by the transmission device, (e.g., the effect of transmission device or network to change the amplitude, phase of or delay in transmission as a function of frequency). Changes in the impedance parameters of the transmission device or in impedances associated therewith change the wave propagation characteristics of the transmission device.
WAVE SHAPING
Passive networks for modifying an electrical wave passing therethrough so that the amplitude-time characteristic of the output wave is different from that of the input wave and which have no function classified in other classes.
WAVE TRANSMISSION DEVICE
Any device which is used to guide or constrain electrical wave energy and to convey the energy from one place to another. Included are conductors, wave guides, resonant structures (e.g., cavities, etc.)
WAVE TRANSMISSION SYSTEM
One of more wave transmission devices with or without appropriate coupling networks or transmission line characteristic modifying means arranged to convey electrical energy from one or more places to one or more other physically separated places. The system may be arranged so that different electrical energies may be conveyed in different directions at the same or different times over the system.
WAVE TRAP
A resonant circuit designed to exclude the energy of one particular frequency. It is analogous to a filter which is used to block one frequency and to pass other frequencies. It usually has circuit components equivalent to a filter, but may be used only to exclude energy of a particular frequency from a circuit.

This subclass is indented under the class definition. Systems comprising (a) two or more wave transmission lines or networks, each line or network being operable to separately propagate wave energy or (b) means for effecting an interchange of wave energy from one transmission line to two or more transmission lines or vice versa, or having a coupling network for effecting an interchange of wave energy from a single input to plural outputs or vice versa, together with means for controlling or facilitating the interchange of energy.
(1) Note. The term "network" as used above denotes any of the systems defined in the Class Definition, subsection A.
(2) Note. Included in (a) above are systems having two distinct transmission lines, each line being operable to transmit wave energy electrically distinct from that propagated by another of the transmission lines, and also lines which are distinct but not necessarily simultaneously usable to transmit electrical wave energy (e.g. one line may be used to substitute for another as in subclass 3). The two or more transmission lines may have a common conductor, see especially subclasses 4+ where a balanced circuit is involved.
(3) Note. Included are lines which transmit energy from a first point to a second spaced point and provided with means to transmit a portion of the energy to a second line (e.g. a tapped line).
(4) Note. This and the indented subclasses do not provide for systems where a signal is divided among two transmission lines or networks and then recombined on a single line or to provide a single output. Such systems and networks are found in subclasses 12 et seq. If the system claimed does not extend to the recombining part of the line or network, the patent is classified in this or the indented subclasses.
(5) Note. A system having a single transmission line and pilot line to sense only ambient conditions (temperature, humidity) is not classified as a plural channel system. See subclass 15 for this subject matter. A system with a single communication transmission line and also a pilot line which is a long line within the class definition and which transmits wave energy is classified in this or indented subclasses.

SEE OR SEARCH THIS CLASS, SUBCLASS:
15 see (5) Note above.

SEE OR SEARCH CLASS:
174, Electricity: Conductors and Insulators, appropriate subclasses for electrical conductor structure adapted for use in plural channel systems other than loaded lines or transmission lines defined as having long line characteristics.
178, Telegraphy, appropriate subclasses for plural channel systems involving telegraphy, note subclass 45 for plural channel systems using a loaded line.
307, Electrical Transmission or Interconnection Systems, particularly 11, 43+, 113+, and 147+ for miscellaneous electrical distribution systems involving plural channels.
330, Amplifiers, subclass 295 for plural channel transistor amplifiers, subclass 69 for sum and difference amplifiers, subclasses 73 and 74 for series arranged amplifiers with plural outputs and plural inputs, respectively, subclass 84 for plural channel amplifiers having feedback, subclasses 124+ for plural channel amplifiers generally, subclasses 147 and 148 for amplifiers having plural inputs and plural outputs, respectively. See especially, subclasses 54 and 286+ for "distributed amplifiers".
334, Tuners, appropriate subclasses for tuners, per se.
439, Electrical Connectors, particularly 775, 865+, 869+, 874+, 877+, 883, and 884+ for various types of electrical connections and terminals.
340, Communications: Electrical, appropriate subclasses for miscellaneous electrical communications, including signalling systems, involving plural channels. Note particularly 870.11, and 870.41, and 870.27 for continuously variable indication communication systems involving plural transmitters, plural receivers, and plural circuits respectively.
343, Communications: Radio Wave, particularly subclass 771 for plural slot type antennas with wave guide coupling; subclasses 814 and 816 for plural balanced doublet type antennas with a coupling network; subclass 852 for antennas with a plural path coupling network with impedance matching; subclasses 853+ for plural antennas with a coupling network; and subclass 858 for antennas coupled to plural leadins.
370, Multiplex Communications, subclass 200 for a phantom circuit, and subclass 308 for a resonant transfer technique used in the multiplex system.
379, Telephonic Communications, appropriate subclasses for plural channel systems involving telephony, see 338 for circuits having a two-way repeater (amplifiers) therein.
455, Telecommunications, 39 for plural channel modulated carrier wave systems; subclasses 91+ for transmitters; subclasses 130+ for plural channel systems in radio receivers; see particularly subclasses 132+ for plural separate receivers; subclasses 3.1+ for distribution systems; and subclasses 272+ for plural separate collecting means.

This subclass is indented under subclass 1. Systems which include gyromagnetic elements for effecting a nonreciprocal interchange of electrical energy among the transmission lines or through the coupling network.
(1) Note. The term "gyromagnetic" as applied to material designates magnetically polarized material (e.g., ferrites, garnets, ionized gases) having unpaired spin systems which exhibit significant precessional motion in an orthogonal R.F. field. The term "nonreciprocal" designates a particular interchange of electrical energy that does not satisfy the reciprocity theorem. For example, a nonreciprocal interchange exists when the electrical output at a first set of terminals of a network produced by an input at a second set of terminals of the network does not equal the output at the second set of terminals produced by the same input applied at the first set of terminals. The term "circulator" (to which most of the patents in this subclass pertain) designates a device with at least three terminals wherein power entering at terminal 1 exists at terminal 2 only, power entering at terminal 2 exists at terminal 3 only, and power entering at terminal 3 exists at terminal 1 only.

SEE OR SEARCH THIS CLASS, SUBCLASS:
24.1 24.2 and 24.3, for single channel coupling networks including gyromagnetic material for effecting a nonreciprocal transfer of electrical energy.

SEE OR SEARCH CLASS:
330, Amplifiers, subclass 4, 4.8 and 63 for amplifiers using gyromagnetic elements.
455, Telecommunications, 318, for mixers using gyromagnetic elements.

This subclass is indented under subclass 1. Plural channel
systems having means to sense a condition in the system and to control the operation of the system in accordance with the condition so sensed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
17 and the subclasses specified in the notes thereto for single channel automatically controlled systems and networks.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnection Systems, particularly subclass 39, 86+, 116+, and 326+ for miscellaneous plural channel electrical transmission or interconnection systems which involve automatic control.
323, Electricity: Power Supply or Regulation Systems, subclasses 234-303 for condition sensing regulators.

This subclass is indented under subclass 2. Systems comprising at least one normally operative wave transmission line and a spare transmission line, and automatically operable means associated with the transmission lines for using the spare transmission line in place of the normally operative transmission line upon failure of the normally operative line.
(1) Note. Systems for automatically substituting a particular device or system for a normally operative device or system are in general classified with the particular device or system. For example, systems for substituting repeaters in a two way repeater system are classified in Class 379, Telephonic Communications, subclasses 338+ and systems for substituting for defective amplifier system or a part of an amplifier system (such as a vacuum tube) are classified with the amplifier systems in Class 330, Amplifiers, subclasses 84 and 124+.

SEE OR SEARCH THIS CLASS, SUBCLASS:
13 for resonator type breakdown discharge systems which control the transmission over a line.
100 for branched circuits with nonautomatic transmission line switching.
262 for transmission line elements, which may include switching devices.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnection Systems, particularly subclass 23, 39, 64+, and 80+ for miscellaneous electrical systems of distribution which involve automatic substitution of electrical load circuits or supply circuits.
331, Oscillators, subclass 49 for plural oscillator systems wherein one oscillator may be substituted for another.

This subclass is indented under subclass 1. Systems wherein at least one of the transmission lines is a balanced line, or having a network under subclass 1 which is especially designed for connection to at least one balanced circuit.
(1) Note. A balanced line or circuit is a line or circuit having its conductors electrically symmetrical with respect to a reference potential plane (e.g. ground).

SEE OR SEARCH THIS CLASS, SUBCLASS:
12 for transmission line inductive or radiation interference reduction systems, involving a balanced transmission circuit.
25 for coupling networks for coupling a single channel balanced circuit to an unbalanced circuit.
236 for single transmission lines of the long line type, which may be balanced.

SEE OR SEARCH CLASS:
174, Electricity: Conductors and Insulators, particularly 32, 37+, 40+, and 68.1+ for electrical conductor structure of the electrically balanced type other than loaded lines or transmission lines defined as having long line characteristics.
307, Electrical Transmission or Interconnection Systems, particularly 12, 42 or 147+ for miscellaneous electrical transmission or interconnecting systems which include balanced circuits.
343, Communications: Radio Wave, subclass 814 and 816 for plural balanced doublet antennas with coupling networks; and subclass 865 for a balanced antenna with a balanced coupling network.
363, Electric Power Conversion Systems, particularly 2, 9+, 36, and 148+ for balanced phase conversion systems for converting electrical energy from one number of phases to a
different number of phases (e.g., single phase to polyphase).
365, Static Information Storage and Retrieval, subclass 202 for complementing or balancing signals used in a read/write circuit.
370, Multiplex Communications, subclass 200 for a phantom circuit used in the multiplex system, and subclasses 278 and 282+ for a duplex system which may include a balance circuit.
379, Telephonic Communications, for telephone systems which involve balanced transmission lines.

This subclass is indented under subclass 4. Systems having a plurality of balanced transmission lines or having a network which is designed for connection to a plurality of balanced circuits.

SEE OR SEARCH THIS CLASS, SUBCLASS:
25 for coupling networks for coupling a single channel balanced circuit to an unbalanced circuit.

This subclass is indented under the class definition. Subject matter including a transmission line producing inductive or radiation interference or subject to such interference from an external source and means such as one or more filters, screens or compensating circuits, disposed along an appreciable length of the line for substantially reducing this interference.
(1) Note. Subclass 12 does not include mere echo or anti-singing systems. Such systems in a single channel system where classified in this class are classified with the first occurring (lowest numbered) subclass providing for any of the components used in the system. For echo-suppressing and/or anti-singing systems in plural channel systems, see subclasses 406+ of Class 379, Telephonic Communications.

SEE OR SEARCH THIS CLASS, SUBCLASS:
5 for plural channel systems, which are balanced to prevent undesired radiation effects.
24 for networks which may be used to reduce undesired currents in a transmission line, and particularly subclasses 138+ for balanced circuits coupled to unbalanced circuits and subclasses 165+ for wave filters and for transmission lines connected to filters which block such undesired currents.
236 for long line transmission line structure which inherently reduce interference radiation effects and which involve no shielding structure or means in addition to the conductor arrangement or structure (e.g. co-axial lines), see especially subclasses 243+.

SEE OR SEARCH CLASS:
174, Electricity: Conductors and Insulators, 32 and the subclasses specified in the notes thereto for structure and conductor arrangements for preventing or reducing the detrimental effects due to either self-inductance of a single conductor or mutual inductance between plural conductors, other than loaded lines or transmission lines defined as having long line characteristics.
178, Telegraphy, subclass 45 for loaded lines with inductive or radiation reduction means, subclass 63, for cable or long line telegraph systems having means for eliminating "tailings" or having static compensation; and subclass 69 for telegraph line clearing and circuit maintenance systems having means for preventing the detrimental effects produced by induction from external or internal causes.
307, Electrical Transmission or Interconnection Systems, 89 for miscellaneous electrical systems having anti-induction means or means to prevent undesired coupling to other systems.
331, Oscillators, subclass 67 for oscillator systems provided with an electromagnetic or electrostatic shield.
343, Communications: Radio Wave, 841 for antennas with an electrical shield; subclass 851 for antennas with a coupling network having a radiation suppressor; and subclass 905 for antennas combined with shielded transmission lines.
361, Electricity: Electrical Systems and Devices, 1 for transmission lines with means to protect the connected lines from the effects of lightning and other high potential, and for networks for use in surge suppression circuits, see especially subclass 50 for systems with means to adjust for varying leakage currents; subclasses 82 and 84+ for systems for protecting balanced electrical systems (e.g., polyphase) for balanced current flowing therein; subclasses 88+ for voltage responsive systems; subclass 111 for transient responsive systems; and subclasses 177+ for high voltage dissipation systems (e.g., lightning arresters).
365, Static Information Storage and Retrieval, subclass 198
for transmission lines used for reading and writing information.
379, Telephonic Communications, subclass 398, for telephone systems having means for preventing the detrimental effects occasioned by induction from external or internal causes.

This subclass is indented under the class definition. Systems which include a resonant device and a space discharge structure positioned at a point of high potential on said resonant device, the space discharge structure breaking down in response to energy above a predetermined level in a transmission line connected to the resonant device to modify the effective electrical characteristics of the resonant device so as to block substantially the flow of any energy over the transmission line, free passage of energy occurring over the line when the energy fails to attain this predetermined level.

SEE OR SEARCH THIS CLASS, SUBCLASS:
2 for plural channel systems which include a resonator type breakdown discharge system for substantially blocking a channel where the discharge device is made conductive by a high energy level in the transmission line, and subclasses 100+ where the discharge device is made conductive by energy other than the energy in the transmission line.
2 14, 15, 16, 17+, and 81, for other systems within the class definition which reduce the amplitude of the wave energy but which do not involve the use of a resonator type breakdown discharge device.
262 for transmission line elements and components which perform a switching or blocking function, other than resonator type breakdown discharge systems.

SEE OR SEARCH CLASS:
313, Electric Lamp and Discharge Devices, 567 for miscellaneous gaseous discharge device structure, including lightning arresters, and subclasses 324 and 325 for lightning arresters of the spark or arc type which operate in the open air.
315, Electric Lamp and Discharge Devices: Systems, subclasses 32-371 for miscellaneous gaseous discharge systems and particularly subclass 39 for the structural combination of a discharge device and a resonant device, i.e., combined in an integral or nonseparable manner.
323, Electricity: Power Supply or Regulation Systems, subclasses 304-317 for self-regulating systems.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 365 for miscellaneous gating circuits which utilize electron tubes.
361, Electricity: Electrical Systems and Devices, 1 for miscellaneous systems for protecting electrical apparatus by opening a circuit or making a shunt or short circuit when the current exceeds a predetermined value, see especially subclass 112 where the system includes electronic tubes, and subclasses 117+ for lightning arrester systems which include an arc discharge device.
455, Telecommunications, 78 for T-R or R-T radio systems.

This subclass is indented under the class definition. Networks including a non-linear device for decreasing the amplitude range of the signal applied to the device, and a nonlinear device connected to receive the wave having the decreased amplitude range for increasing or restoring the amplitude range of the signal, and long line transmission lines in combination with such networks.
(1) Note. This subclass provides for amplitude compression and expansion systems even though the system includes an active element such as a vacuum tube type amplifier. See (3) Note below.
(2) Note. This subclass does not include devices which merely shift the amplitude level up or down merely to control the peak amplitude without controlling the amplitude range. Neither does this subclass include the combination of a limiter or clipper and an amplifier which cuts off the higher amplitudes and then amplifies the remaining portion of the wave energy so that the output wave does not contain any variations in wave form above a certain amplitude level, and is not therefore a function of the input wave energy.
(3) Note. In the compressor portion of the compander, the input waves of smaller amplitudes may be increased in amplitude while the input waves of larger amplitude may be increased by a smaller ratio or decreased. All amplitudes of the wave may be decreased, the larger amplitudes being decreased to a smaller extent. The expander portion may operate in a similar manner except to increase the amplitude range.

SEE OR SEARCH THIS CLASS, SUBCLASS:
20 for miscellaneous passive type wave shaping networks which modify the amplitude time characteristic of the signal transmitted therethrough.
81 for the attenuator network in this class which reduces the energy of the signal passing therethrough.

SEE OR SEARCH CLASS:
178, Telegraphy, subclass 45, for loaded lines in combination with a compander.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 309 for a miscellaneous limiter with an amplifying circuit.
330, Amplifiers, subclass 96, 123 and 129+ for amplitude range compressors or expanders of the amplifier type where the input signal is applied to a control grid of an amplifier tube whose bias is controlled in accordance with the signal intensity to produce the necessary compression or expansion, and wherein the output signal is abstracted from the plate of the amplifier tube. Subclasses 143 and 144+ for compressors or expanders where a variable impedance element is included in the signal path and the variable impedance is controlled in accordance with the signal intensity. The combination of an amplitude compressor and expander (i.e., a compander) one or both being of the amplifier type is classified in this class, (333) subclass 14. However, where such combinations involve correction only of an amplifier condition and not a condition of the transmission line, classification is with amplifiers Class 330. Combinations of an amplifier and a limiter where the output more substantially conforms to the input wave form are classified in Class 330. See Class 250, subclass 27, above.
369, Dynamic Information Storage or Retrieval, subclass 133 for phonograph recording and reproducing systems involving amplitude range compression and expansion.
370, Multiplex Communications, subclass 202 for a multiplex system which includes an amplitude compression or expansion means.
381, Electrical Audio Signal Processing Systems and Devices, subclass 106 for one-way audio signal transmission having amplitude compression/expansion.
704, Data Processing: Speech Signal Processing, Linguistics, Language Translation, and Audio Compression/Decompression, 500 for systems changing the frequency range of a band of audio signal frequencies, transmitting the energy at the changed range, and restoring the transmitted audio signal to its original frequency range.

This subclass is indented under the class definition. Systems including an auxiliary line so structurally related to a transmission line that a change in the transmission line characteristics caused by a change in an ambient condition, such as temperature or humidity, will be accompanied by a change in a parameter of the auxiliary line, and means controlled by this change in parameter to compensate for the change in transmission line characteristics.

SEE OR SEARCH THIS CLASS, SUBCLASS:
2 for plural channel systems including a pilot line.
16 for systems utilizing a pilot current for purposes of control.

SEE OR SEARCH CLASS:
323, Electricity: Power Supply or Regulation Systems, subclass 294 for impedance systems in general which are automatically controlled in response to a thermal condition.
330, Amplifiers, subclass 52, for amplifier systems having control means, wherein the control is exercised by a pilot signal. See the Class Definition of Class 330 for the line between this class (333) and Class 330 where pilot signals are involved.
379, Telephonic Communications, 338 for repeater systems (e.g. two way amplifier system) which utilize a pilot line to compensate for changes in the transmission characteristics of the main line.

This subclass is indented under the class definition. Systems including means for compensating for changes in the signal energy passing over a transmission line caused by changes in the line characteristics, wherein a control signal distinct from and in addition to the signal energy is also passed over the line to be influenced by the changes in line characteristics, the control signal being used to control the compensating means.
(1) Note. Systems for automatically compensating for changes in the characteristics of a transmission line where the carrier current of the transmitted energy is used to control the compensating means are classified in subclasses 17+.

SEE OR SEARCH THIS CLASS, SUBCLASS:
2 for plural channel systems utilizing a pilot frequency.
15 for systems utilizing for a pilot line for control purposes.
17.1 see (1) Note above.

SEE OR SEARCH CLASS:
330, Amplifiers, subclass 52 for amplifier systems having pilot signal control means. See Class 330, Class Definitions for the line between the two classes where such subject matter is involved.
379, Telephonic Communications, 338 for repeater systems (e.g., two way amplifier system) which may utilize a pilot current to compensate for changes in the transmission characteristics of the main line.

AUTOMATICALLY CONTROLLED SYSTEMS:
This subclass is indented under the class definition. Subject matter having means to sense a condition in the system and to modify a wave propagation characteristic of the system in accordance with the condition so sensed.
(1) Note. The automatic control must be of the wave propagation characteristic of a transmission line, system or network which would be classified in this class. Where the system or network includes a component or device which, per se, is not classified in the class, combined with a transmission line, system or network which causes classification of the subject matter in this class, and the automatic control is only with respect to such component or device which is classified, per se, in another class. Then the patent is not classified in this or the indented subclass, but is classified in subclass providing for the subject matter claimed. For example, a wave filter combined with an automatically operated current or voltage magnitude control means does not effect the wave propagation characteristic of the filter are classified in subclasses 165+ below.

SEE OR SEARCH THIS CLASS, SUBCLASS:
2 for plural channel systems including automatic control.
13 for resonator type breakdown discharge systems which are automatically controlled.
14 for amplitude compression and expansion systems including automatic control.
15 for pilot line controlled systems involving automatic operation.
16 for pilot current controlled systems including automatic operation.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnection Systems, appropriate subclasses, especially 92, 97, 99, and 116 for miscellaneous electrical distribution systems with automatic control means.
323, Electricity: Power Supply or Regulation Systems, subclasses 234-303 for condition sensing regulators.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 509 and 518+ for miscellaneous externally effected or control circuits.
331, Oscillators, 1 for oscillator systems utilizing a phase or frequency sensing means for automatically stabilizing the oscillator frequency subclass 183 for oscillator systems having means for automatically controlling or stabilizing the amplitude of the generated oscillations and subclass 186 for oscillator systems with a particular source of power or bias voltage of the automatically regulated type.
336, Inductor Devices, particularly 30 for inductor devices automatically adjustable in response to a condition.

Limiting of Amplitude:
This subclass is indented under subclass 17.1. Subject matter including means to limit the amplitude to a predetermined level.

SEE OR SEARCH THIS CLASS, SUBCLASS:
81 for systems and networks that selectively lower the input signal level to a desired amount.

SEE OR SEARCH CLASS:
307, Electrical Transmission or Interconnection Systems, subclass 264 and 540+ for limiting the amplitude of pulses in nonlinear solid state circuits.

Impedance Matching:
This subclass is indented under subclass 17.1. Subject matter in which the condition sensed is utilized to control circuitry that performs an impedance matching function in the system.

SEE OR SEARCH THIS CLASS, SUBCLASS:
32 for impedance matching circuits of the nonautomatically controlled type.

SEE OR SEARCH CLASS:
455, Telecommunications, 120 for frequency tuning a transmitter to an antenna.

This subclass is indented under subclass 17. Systems and networks provided with automatically operated means to control an equalizer and delay network.
(1) Note. This subclass includes systems including an equalizer and/or a delay network which is automatically controlled in response to some condition in the system and also equalizers and/or delay networks which are provided with other automatic control means.

SEE OR SEARCH THIS CLASS, SUBCLASS:
12 for automatic equalization and/or delay control networks utilized for preventing, suppressing or eliminating interference.
15 for automatic equalization and/or delay control networks controlled by the signal derived from a pilot line.
16 for automatic equalization and or delay control networks involving a pilot current control.
28 for nonautomatic equalizers.
138 for nonautomatic delay networks.

SEE OR SEARCH CLASS:
323, Electricity: Power Supply or Regulation Systems, subclasses 212-219 for automatic phase control systems involving a single frequency.
363, Electric Power Conversion Systems, 2, 9+ and 36 for plural conversion systems involving phase conversion; subclasses 148+ for phase conversion systems, per se; particularly subclass 149 for phase conversion systems involving automatic voltage magnitude or phase angle control.

This subclass is indented under the class definition. Passive networks for producing an output wave which is the time derivative or time integral of the input wave.
(1) Note. See the internal and external search notes under subclass 20 of this class for wave shaping systems which may involve differentiating and/or integrating networks.

SEE OR SEARCH THIS CLASS, SUBCLASS:
20 for passive networks for shaping the output wave to other than the time derivative or time integral of the input wave. Also see (1) Note above.

SEE OR SEARCH CLASS:
318, Electricity: Motive Power Systems, 609 and 611+, particularly subclasses 621+ for position servomechanisms which include stabilizing control features such as integrating and differentiating networks; subclasses 141+ for generator fed motor systems having generator control including anti-hunt or rate of change response; subclass 702 for synchronous motor systems having anti-hunt or anti-damping control; subclass 448, for open loop automatic motor control systems involving anti-hunt control; and subclasses 456+ for systems responsive to the rate of change of a condition.
322, Electricity: Single Generator Systems, subclass 19 for systems for automatically controlling the rate of change or hunting of a generator or its driving means.
323, Electricity: Power Supply or Regulation Systems, subclasses 212-219 for miscellaneous phase control networks which involve differentiating or integrating networks.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, subclass 335 for miscellaneous differentiating circuits and subclasses 336+ for miscellaneous integrating circuits.
708, Electrical Computers: Arithmetic Processing and Calculating, subclass 822 and 823+ for calculators performing computations involving differentiation and
integration, respectively.

This subclass is indented under the class definition. Passive networks for modifying an electrical wave passing therethrough so that the amplitude time characteristic of the output wave is different from that of the input wave and which have no function classified in other classes, and long line wave transmission systems in combination with a passive wave shaping network.
(1) Note. The networks are usually designed to modify or shape a single pulse and usually involve a delay network or equivalent delay means.
(2) Note. Included are long transmission lines in combination with a wave shaping network which is designed to restore the wave shape to a wave which has been distorted by transmission over the transmission line.
(3) Note. Excluded are mere limiter networks which shape the wave merely by cutting off the wave above a predetermined amplitude.
(4) Note. Many systems and networks inherently function to wave shape. Most of these systems are excluded as they include active elements, such as oscillation generators, amplifiers, detectors, etc. Where the network is primarily designed for a purpose other than wave shaping, such as controlling the magnitude of current in the circuit, the network is excluded even though the control of the current magnitude is effected by a means which also effects the wave shape of the element.

SEE OR SEARCH THIS CLASS, SUBCLASS:
1 for systems combining wave energy from different channels and/or separating wave energy into different channels.
14 for amplitude range compression and expansion systems.
19 for wave shaping networks producing a time derivative or time integral of the applied wave energy (i.e. differentiating or integrating networks).
28 for networks modifying the attenuation or attenuation and phase characteristic with respect to frequency of the energy passing therethrough (i.e. equalizers).
81 for attenuator networks.

SEE OR SEARCH CLASS:
84, Music, 622, 626+, 659+, 671 - 677 and 692 - 711 for systems for the electrical production of complex waves in musical instruments.
178, Telegraphy, 2, and particularly subclasses 63, 69 and 69.1 for telegraph systems involving combining and/or separating and/or shaping of electric waves.
307, Electrical Transmission or Interconnection Systems, 106 for waveform or wave shape determinative or pulse producing systems which are class appropriate. The networks and systems in Class 307 may involve long line elements, but ordinarily include also a specific source of wave energy or pulse producing means, such as a DC source and switching means.
324, Electricity: Measuring and Testing, 76.12 for electrical systems for the analysis of complex waves, and subclasses 76.39+ for electrical frequency measuring systems which involve wave analysis.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 100 for miscellaneous converting, shaping, or generating circuits such as miscellaneous limiters and clock or pulse production circuits.
330, Amplifiers, 53 for amplifier systems combined with a long line element, where the amplifiers may correct for the distortions caused by the long line.
331, Oscillators, 75 for oscillator systems combined with an output circuit including a space discharge or unilaterally conductive device, which device may provide a wave distorting or shaping function.
332, Modulators appropriate subclasses for modulator systems which involve wave shaping.
340, Communications: Electrical, 825.77 for selective electrical communication systems wherein the selective means is responsive to the amplitude of the signal.
363, Electric Power Conversion Systems, appropriate subclasses for conversion systems which involve wave shaping, see 34 for systems for converting A.C. to D.C. and then connecting the D.C. to A.C., subclasses 39+ for conversion systems with means to introduce or eliminate frequency components, and subclasses 157+ for frequency conversion systems. The systems in Class 363 usually involve the use of alternating current which is repetitive and do not involve the shaping of a single pulse.
379, Telephonic Communications, appropriate subclasses for telephone systems involving combining and/or separating and/or shaping of electric waves.

This subclass is indented under the class definition. Wave transmission systems comprising means for changing guided waves having one field configuration to a different field configuration, the original and changed waves each having a longitudinal electric or magnetic field component.
(1) Note. This subclass includes means for changing a rectangular TE wave pattern to a circular TE wave pattern, e.g. for changing a plane polarized guided wave to a circularly polarized guided wave, or from one type of polarized wave to another.

SEE OR SEARCH THIS CLASS, SUBCLASS:
248 for mode filters or suppressors, and for wave guide junctions (e.g. rotary joints involving mode conversion and reconversion).

SEE OR SEARCH CLASS:
343, Communications: Radio Wave, subclass 756 for antennas with a polarization converter; and subclasses 909+ for radio wave polarizers, per se.

This subclass is indented under the class definition. Networks specialized for use with and designed for connection to the end of a long line transmission line and including a resistive component for dissipating the wave energy propagated along the line and presenting an essentially resistive impedance to the line, and the combination of long transmission lines with energy dissipating terminations.
(1) Note. Usually the impedance presented by the network is equal to the characteristic impedance of the line for which it is designed.
(2) Note. The termination classified here is usually more than a mere resistance element such as is classified in Class 338, Electrical Resistors. The termination includes some structure, such as a long line element or component, so that the device is not of general utility, but is limited to use with a transmission line. Long lines with mere resistance elements which would, per se, be classified in Class 338, are included in this subclass (22) when the resistance element is designed for use as a long line dissipating termination.

SEE OR SEARCH THIS CLASS, SUBCLASS:
23 for networks simulating transmission lines (i.e. artificial lines) whose function is not essentially dissipating terminal energy.
32 for impedance matching networks whose function is coupling as opposed to termination.
81 for attenuators, which dissipate only a portion of the wave energy applied thereto.

SEE OR SEARCH CLASS:
343, Communications: Radio Wave, subclass 18 for radio wave absorption devices; subclasses 731+ for traveling wave type antennas which may involve a dissipating termination; and subclasses 739+ for antennas with a terminating resistance at open end.
361, Electricity: Electrical Systems and Devices, 117 for surge dissipators and lightning arresters.

This subclass is indented under the class definition. Networks for simulating impedance characteristics of a smooth or loaded electrically long transmission line over a frequency range.

SEE OR SEARCH THIS CLASS, SUBCLASS:
22 for dissipating terminations for long lines which usually have an impedance characteristic equal to the characteristic impedance of the line.
28 for equalizing networks having impedance characteristics usually the inverse of electrically long transmission lines.
81 for attenuators.

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330, Amplifiers, subclass 57, for amplifiers utilizing artificial lines. (This also includes the "distributed amplifiers").

This subclass is indented under the class definition. (1) Networks including significant reactive structure for effecting the transfer of oscillator energy from one circuit to another circuit and having attenuation and/or delay characteristics over a frequency range for attenuating and/or delaying in a predetermined manner, wave energy passing therethrough, and/or providing an impedance match between the network and at least one of the circuits; (2) smoothing type wave filters having shunt capacitance, or series inductance, or both usually designed to pass direct current and to reduce the effect of any undesired alternating or pulsating current, or to pass direct current and low frequency alternating current or pulsating current and to reduce the effect of any undesired higher frequency alternating or pulsating current, and (3) systems within the class definition including one or more of the networks defined in (1) or (2) above.
(1) Note. The coupling networks under the above definition usually include a shunt impedance common to the input and output circuits.
(2) Note. The systems included are single channel systems having coupling networks, and include for example echo suppression on a single channel where the echo would be due to an impedance mismatch, or the elimination of echo in a single channel system by using a delay line. Such systems are classified in the first indented subclass which provides for the network used in the system. See section I, subsection C, of the Class Definition.
(3) Note. Class 323, Electricity: Power Supply or Regulation Systems, is the miscellaneous class for systems for coupling a single source to a single load circuit using only transformers and/or impedances. Also, see (4) Note below.
(4) Note. Coupling networks using an electronic tube as a part of the network are not included in this or the indented subclass, but are classified in the appropriate class providing for the system. For examples, see the Search Class notes below.
(5) Note. See the Search Class notes below for a reference to the classification lines between coupling networks and antennas combined with such coupling networks.

SEE OR SEARCH THIS CLASS, SUBCLASS:
1 for plural channel systems involving coupling networks.
17 for automatically controlled systems involving coupling networks.
81 for attenuators of the resistive type.
245 for transmission line joints within the class definition
which do not modify the characteristics of the wave propagated therethrough or do not effect an impedance match between dissimilar impedance lines or networks.

SEE OR SEARCH CLASS:
178, Telegraphy, appropriate subclasses for coupling networks in combination with code signaling systems or apparatus other than telephony. See subclass 64 for such systems for transmitting messages by induced currents utilizing an induction coil or transformer, and for such systems having an induction coil or transformer between sections of the main line.
307, Electrical Transmission or Interconnection Systems, particularly 1 for miscellaneous superimposed current systems involving coupling networks, and subclasses 11+ and 43+ for miscellaneous plural load or plural supply systems which include coupling networks.
323, Electricity: Power Supply or Regulation Systems. See (3) Note, above. Class 323 provides for the miscellaneous transformer and impedance systems and includes structural combinations of different impedances which are electrically connected together.
323, Electricity: Power Supply or Regulation Systems, for a coupling network using tubes to control the current and/or voltage magnitude and/or for phase control where there is a single input and output and at least a part of the input energy appears in the output circuit. (See the (4) Note above)
327, Miscellaneous Active Electrical Nonlinear Devices, 261 for a delay system using tubes; subclasses 552+ for a filter using tubes; subclass 231 for a phase shifter using tubes where the input energy is applied to an input electrode (e.g., grid) of the tube to control a local source of energy (e.g., anode supply) connected to the output electrode of the tube (See the (4) Note above)
330, Amplifiers, appropriate subclasses for various types of coupling networks involved in amplifier systems, subclass 116 for an amplifier system with means to couple a balanced line to an unbalanced line. (See the (4) Note above)
331, Oscillators, 74 for oscillation generators combined with a particular output coupling network.
334, Tuners, for tuners, per se. See also (4) Note above for tuners combined with other systems.
336, Inductor Devices, appropriate subclasses for the structure of transformers and inductances of the passive type.
343, Communications: Radio Wave, subclass 743 for high
frequency loop type antennas with feed coupling at spaced points on the loop; subclass 771 for slot type antennas with wave guide coupling; subclasses 814, 816 and 820+ for balanced doublet type antennas with a coupling network, subclasses 850+ for antennas in general with a coupling network or impedance in the leadin; subclass 700, (11) Note, for the classification lines between coupling networks and antennas combined with such coupling networks (see the (5) Note above).
361, Electricity: Electrical Systems and Devices, 600 for miscellaneous combinations of different impedances which are not in circuit relationship (e.g., a variable condenser combined with a resistance with no electrical connection between them).
379, Telephonic Communications, appropriate subclasses for telephone systems having coupling networks. If the system is limited to use with speech (other than by mere name), such as including a microphone or reproducer (e.g., loudspeaker) the system is classified in Class 381, see 338 for repeaters utilizing hybrid coil systems.
455, Telecommunications, 91 for radio transmitters involving coupling networks and subclasses 130+ (particularly subclasses 338+) for radio receivers involving coupling networks.

This subclass is indented under subclass 24. Networks which include gyromagnetic elements for effecting a nonreciprocal transfer of oscillatory energy from one circuit to another circuit.
(1) Note. See (1) Note under subclass 1.1 above for a definition of the terms "gyromagnetic" and "nonreciprocal". Many of the patents in this generic subclass 24.1 are directional phase shifters, and relate to networks that shift the phase of energy passing through by different amounts depending on the direction of passage.

SEE OR SEARCH THIS CLASS, SUBCLASS:
1.1 for plural channel nonreciprocal gyromagnetic systems. See also (1) Note above.
138 for delay networks generally.
202 for waveguide filters generally.

SEE OR SEARCH CLASS:
324, Electricity: Measuring and Testing, 300 for nuclear or electronic induction measuring or testing devices.
330, Amplifiers, subclass 4, 4.8 and 63 for amplifiers using gyromagnetic elements.
455, Telecommunications, subclass 323 for mixers using gyromagnetic elements.

This subclass is indented under subclass 24.1. Networks wherein the attenuation in one direction of propagation through the network is substantially greater than in the opposite direction.
(1) Note. The attenuation in one direction may be substantially zero.

SEE OR SEARCH THIS CLASS, SUBCLASS:
81 for attenuators generally.

This subclass is indented under subclass 24.1. Networks wherein the polarization of the electric vector of the wave energy propagated through the network is rotated in the same absolute sense for both directions of propagation.
(1) Note. Included in this subclass are the so-called anti-reciprocal or Faraday rotators.

SEE OR SEARCH THIS CLASS, SUBCLASS:
248 for rotators generally.

This subclass is indented under subclass 24. Networks including four terminals, the impedance across one pair of terminals being symmetrical and the impedance across another pair of these terminals being unsymmetrical with respect to a given potential plane (e.g., ground), these impedances being effective to convert symmetrical potential applied at the
symmetrical pair of terminals to unsymmetrical potential at the other pair of terminals or to convert unsymmetrical potential applied at the unsymmetrical pair of terminals to symmetrical potential at the other pair of terminals, and systems under the class definition including a balanced to unbalanced circuit coupling.

SEE OR SEARCH THIS CLASS, SUBCLASS:
1 for plural channel systems, which involve coupling a balanced circuit to an unbalanced circuit or vice versa.
12 for systems for reducing inductive or radiation interference and which include coupling between balanced and unbalanced circuits.

SEE OR SEARCH CLASS:
323, Electricity: Power Supply or Regulation Systems, subclasses 212-219 for phase control systems with means to introduce delay into a part of the system, and including such systems using reactive impedances and transformer systems to obtain a phase shift (e.g., a 1805 shift) and which are designed for use at a single frequency.
329, Demodulators, appropriate subclasses for demodulators having inputs or outputs which are balanced or unbalanced.
330, Amplifiers, subclass 275 and 301 for transistor amplifiers with balanced-to-unbalanced coupling and vice versa, subclass 116 for amplifier systems having balanced-to-balanced coupling, and subclass 117 for amplifier systems having unbalanced-to-balanced coupling.
343, Communications: Radio Wave, subclass 821 for balanced doublet type antennas with a balanced to unbalanced coupling network; and subclass 859 for antennas in general with a balanced to unbalanced coupling network.
363, Electric Power Conversion Systems, 2, 9+, 36, and 148+ for systems converting energy from one number of phases to a different number of phases.

This subclass is indented under subclass 25. Balanced to unbalanced circuit coupling networks and systems where the coupling network includes a long line element.

SEE OR SEARCH THIS CLASS, SUBCLASS:
236 for long lines.
245 for long line elements.

This subclass is indented under subclass 24. Coupling systems having a long line with a coupling network at each opposed ends of the long line.
(1) Note. Where the long line is merely a part of a coupling network, and does not link two different coupling networks together, classification is not in this subclass. See subclasses 156+ for this type of delay network, subclasses 50+ for this type of impedance matching network, 202+ for this type of wave filter.
(2) Note. In this subclass are systems having two coupling networks with a long transmission line connected to transmit energy from one network to the other. These systems approach a complete system. For example, a 70 ohm source connected by a network to a 300 ohm line which is coupled by a network to a 150 ohm receiver. At each point of connection there would be a coupling network.

SEE OR SEARCH THIS CLASS, SUBCLASS:
50 see (1) Note above.
156 see (1) Note above.
202 see (1) Note above.
236 for long lines, per se.

SEE OR SEARCH CLASS:
178, Telegraphy, appropriate subclasses where the system is limited to code signaling other than telephony.
330, Amplifiers, 53 for amplifier systems combined with long lines or long line elements wherein such means furnish a coupling means for the amplifier.
379, Telephonic Communications, 90 for composite telephone systems (e.g., combined power and telephone circuit) and subclasses 338+ for two telephone lines with two-way repeaters at spaced points along the line.
381, Electrical Audio Signal Processing Systems and Devices, 82 for public address and similar systems (e.g., a microphone and a line, or a line and a reproducer such as a loudspeaker or a microphone, a line and a reproducer).

This subclass is indented under subclass 24. Networks with attenuation or attenuation and phase distortion characteristics which vary over a frequency range for use in a wave transmission system for modifying the attenuation or attenuation and phase characteristics of the wave energy as a function of frequency, and systems within the class definition which include such networks.
(1) Note. Equalizer networks are used to reduce the attenuation or attenuation and phase distortion characteristics which the wave energy in a long line transmission system would have in the absence of the network. The network may be used for predistorting so that the distorting effect of the long line will be corrected.
(2) Note. A filter is distinguished from an equalizer in that a filter is intended and designed to transmit a frequency or one or more bands of frequencies without modification while undesired frequencies are attenuated to a low value so that the desired frequency or frequencies are transmitted by the filter and the undesired frequencies are substantially blocked, while the equalizer has the function of changing the relative amplitudes of the waves of different frequency over the range of frequencies transmitted by the equalizer.
(3) Note. Included are tone control networks which involve only passive elements and which vary the attenuation or attenuation and phase distortion characteristics over a range of frequencies. Included are such networks as are used for "bass boosters", "treble boosters", "treble cut systems", etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:
18 for this subject matter where the equalizer is provided with automatic control means.
20 for wave shaping systems.
81 for attenuator networks within the class definition composed entirely of resistive elements.
138 for phase control or delay networks, per se.

SEE OR SEARCH CLASS:
323, Electricity: Power Supply or Regulation Systems, appropriate subclasses for miscellaneous impedance and transformer systems, and for phase control systems.
330, Amplifiers, appropriate subclasses, particularly
subclass 109, 120, 122, 154, 157+, 185+, 192+, and 304, for amplifier systems combined with an equalizer network.
332, Modulators, subclass 107 for distortion control in pulse modulators, subclasses 123+ for distortion control in frequency modulators, subclasses 144+ for distortion control in phase modulators, and subclasses 159+ for distortion control in amplitude modulators.
381, Electrical Audio Signal Processing Systems and Devices, 98 for audio signal processing devices and systems having frequency control.
455, Telecommunications, subclass 267 for radio receivers with tone control networks.

This subclass is indented under subclass 24. Coupling networks which include one or more impedance elements constructed or proportioned to substantially eliminate the reflected wave energy between the network and at least one of the connected circuits caused by impedance differences; impedance matching networks, per se; and systems within the class definition which include such networks.
(1) Note. The particular construction or proportioning producing the impedance match should be claimed for classification in this subclass.
(2) Note. The impedance need only to be matched to pass the energy or frequency band of energy desired.

SEE OR SEARCH THIS CLASS, SUBCLASS:
8 for branched plural channel systems having impedance matching.
17 for systems wherein the impedance match is automatically controlled.
22 for line terminations involving impedance matching.
81 for attenuators having means for compensating for changes in terminal impedance caused by adjustment of the attenuator so as to match the impedances of the attenuator to the connected input and/or output circuit.
236 for long lines wherein reflected wave energy arising from the line structure is compensated.

SEE OR SEARCH CLASS:
324, Electricity: Measuring and Testing 600, especially subclasses 612+ for the miscellaneous measurement and testing of impedance mismatch between circuits, and subclass 140+, for systems and apparatus for the measurement of voltage, current or power ratios which are indicative of impedance mismatch.
343, Communications: Radio Wave, subclass 822 for balanced doublet type antennas with an impedance matching coupling network; and subclasses 860+ for antennas in general with an impedance matching coupling network.

This subclass is indented under subclass 32. Impedance matching networks and systems including a long line element.

SEE OR SEARCH THIS CLASS, SUBCLASS:
236 for long lines.
245 for long line elements.

SEE OR SEARCH CLASS:
343, Communications: Radio Wave, subclass 862 for antennas with an impedance matching coupling network including a long line element.

This subclass is indented under subclass 33. Impedance matching networks and systems wherein the long line element lies along the path of wave propagation through the network and has a physical dimension progressively increasing or decreasing along the path of propagation to result in a corresponding change in electrical parameters of the long line element.

SEE OR SEARCH CLASS:
343, Communications: Radio Wave, subclass 863 for antennas with an impedance matching coupling network including a tapered long line element.

This subclass is indented under subclass 33. Impedance matching networks and systems wherein the component having distributed electrical parameters lies along the path of wave propagation through the network and is an odd integral number of quarter-wave lengths long.

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343, Communications: Radio Wave, subclass 864 for antennas with an impedance matching coupling network including a long line element of the quarter-wave transformer type.

This subclass is indented under the class definition. Devices and networks consisting of one or more elements which exhibit only a positive resistance effect and which reduce the intensity of the energy passing through the device by dissipation, (1) the elements being proportioned to permit a change in their value to control the energy loss while maintaining substantially constant input and/or output impedance of the device, and/or (2) the elements being proportioned to permit the device to be inserted in the circuit to provide an energy loss without introducing any reflections in the circuit, and/or (3) the elements being combined with a long line or long line element, and/or (4) the device or network having an impedance equal to the impedance of a specified long line and/or (5) the device or network is claimed as being particularly modified for use over a frequency band so that its characteristics are particularly related to frequency, and (6) systems within the class definition including such devices or networks.
(1) Note. The networks and devices of part 5 of the definitions may include means such as capacitors to compensate for deviations in attenuation caused by changes in frequency of the applied energy, so that the device or network acts as a pure resistance. The network or device may be modified to obtain uniform attenuation over a band of frequencies.
(2) Note. Included are T, H, pad, and ladder or lattice type networks as well as transmission line sections.
(3) Note. This subclass embraces devices wherein one or more of the elements include reactance to compensate for any inherent reactance of the element or elements, see (1) Note.
(4) Note. If the device or network does not maintain a constant input and/or output impedance, or if it would introduce reflections into the transmission line, it is
excluded from this class and will be found in Class 323 Electricity: Power Supply or Regulation Systems.

SEE OR SEARCH THIS CLASS, SUBCLASS:
13 for resonator type breakdown discharge systems, which include attenuation networks.
14 for amplitude compression and expansion systems which include attenuation networks.
15 and 16, for pilot controlled systems which include attenuation networks.
17 for automatically controlled systems which may include attenuation networks.
22 for transmission line terminations which dissipate the applied energy.
24 for adjustable reactive type coupling networks in general, see especially subclass 28 for equalizer networks.

SEE OR SEARCH CLASS:
181, Acoustics, appropriate subclasses, for devices for attenuating sound, see subclass 206 for mufflers.
323, Electricity: Power Supply or Regulation Systems, see (4) Note above.
330, Amplifiers, appropriate subclasses under 157+, 185+ and 192+ for amplifiers having significant coupling which may include attenuators.
338, Electrical Resistors, appropriate subclasses, for electrical resistors, per se; and 68 for mechanically variable resistors including potentiometers and rheostats.

This subclass is indented under the class definition. Subject matter which is not provided for in any of the preceding subclasses in this class.

Having branched circuits:
This subclass is indented under subclass 1. Systems including means for effecting an interchange of wave energy
from one transmission line to two or more transmission lines, or vice versa, or having a coupling network for effecting an interchange of wave energy from a single input to plural outputs, or vice versa, of energy together with means for controlling or facilitating this interchange of energy.

SEE OR SEARCH THIS CLASS, SUBCLASS:
2 for plural channel branched circuit systems having automatic controlled means to control the system.
4 for plural channel systems and coupling networks wherein at least one of the transmission lines is a balanced line or where the network is especially designed for coupling to at least one balanced line.
13 for resonator type breakdown discharge circuits which include a space discharge device designed to breakdown in response to high level energy (e.g., from the transmitting section of the system) to block substantially the flow of high level energy, and to pass low level energy along the transmission line (e.g., to a receiver). The devices in subclass 13 include T-R and R-T systems.

SEE OR SEARCH CLASS:
174, Electricity: Conductors and Insulators, particularly subclass 38, 43, 49, and 71+ for branched electrical conductor structures other than loaded lines and conductors defined as having long line characteristics.
307, Electrical Transmission or Interconnection Systems, particularly 11, 43+, and 147+ for miscellaneous electrical distribution systems which include branched circuits.
327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems, 407 for miscellaneous circuits for use in coupling plural channels to a single channel.
331, Oscillators, 60 for an electrical oscillation generator provided with plural output circuits.
343, Communications: Radio Wave Antennas, subclass 771 for plural slot-type antennas with wave guide coupling; subclasses 776+ for plural waveguide type antennas with coupling; subclasses 814 and 816 for plural balanced doublet type antennas with a coupling network; subclasses 853+ for plural antennas generally with a coupling network; subclass 858 for antennas coupled to plural lead-ins.
375, Pulse or Digital Communications, 268, 353 for duplex systems having an antenna coupling network coupling a transmitter and a receiver to an antenna.
439, Electrical Connectors, 150 and 242 for multiple connector structure; subclasses 241+ for line tapper connector structure such as alligator clips and test probes.
455, Telecommunications, 132 for antenna coupling networks for plural receivers where the coupling network includes an active element and/or significant receiver structure; and subclasses 103+ for similar subject matter for transmitters.

Including switching means:
This subclass is indented under subclass 100. Systems with means for abruptly connecting and disconnecting two or more transmission lines to or from another transmission line.
(1) Note. The systems in this subclass usually having means to reduce reflected waves resulting from impedance discontinuities or irregularities caused by the presence or operation of the connecting and disconnecting means.
(2) Note. Plural circuit switches restricted to use in a particular art are sometimes classified with the art, for example, switches in telegraph systems and switches in telephone systems are classified elsewhere.
(3) Note. Variable power dividers which are classified below normally have a continuously variable transfer of power which is not abrupt.

SEE OR SEARCH THIS CLASS, SUBCLASS: <