This class includes patents relating to the following means for the safeguard and control of traffic upon or across railways (that is, fixed tracks for occupant- controlled vehicles) or which by structure are especially adapted for such use, viz.:
A. Signals, including those used for communication between occupants of a car or train.
B. Indicators, recorders, teles:graphic, telephonic, or other similar apparatus when especially designed for use in connection with car or train movements, except manually-set devices, such as train and engine signs and markers capable of general use.
C. Devices on the roadway, such as signals, switches, circuit closures, gates, etc., actuated or controlled from or by the moving vehicles, except circuit-controllers actuated
by the vehicle for the purpose of energizing sectionalized conductors used for supplying propulsion-current thereto.
D. Automatic train stop and speed control means, the actuation of which is initiated by agencies not on the train or by wheel derailment or defects in train structure and mechanism, the automatic stop, for classification purposes, being considered an equivalent of and substitute for a railway signal; but train stopping and control mechanism cooperating with obstacles fixed in position upon the track which have no moving parts are excluded from this class except when they cooperate with speed-responsive devices on the train.
E. Safety devices, including derailing switches and blocks, used for preventing accidents caused by the misplacement of switches, disregard of signals etc.
F. The structure of signals, switches, frogs, and crossings and their appurtenances.
G. Mechanism for the manual or other actuation of any of the devices of the class.
INDEX TO TECHNICAL LITERATURE
In many of the subclasses there have been placed upon the official search-cards references to such literature as appears to relate to the subject-matter of such subclass; but no attempt has been made to make these references complete. It has not been deemed advisable to print these references in connection with the respective subclass definitions; but they can be inspected in the Public Search-Room in connection with the Chief Draftsman's classified copies of patents. The list of works indexed is given below.
Literature in Scientific and Technical Information Center
Alternating Current Signaling, 1915, The Union Switch and Signal Co., Swissvale, Pa. Automatic Block Signal and Signal Circuits, Scott, New York, 1908. Block and Interlocking Signals, Elliott, New York,1896. Block System of Signaling on American Railroads, The, Adams, New York, 1901. First to Fifth Annual Reports Block Signal and Train Control Board, Interstate Commerce Commission,1909 to 1913. Locking, Laverack, New York, 1907. Mechanical Railway Signaling, second edition, Wilson, London, about 1909. Notes on Track Construction and Maintenance, Camp, Chicago, 1903. Perfect Railway Signaling, Spang, 1902. Power Railway Signaling, Wilson, 1908. Railroad Signal Dictionary, The, Adams & Hitt, New York, 1908. Railroad Signal Dictionary, The revised edition, New York, 1911. Railway Appliances, Barry, New York, 1896. Railway Block Signaling, Pigg, London. Railway Engineer, The, (about 1909). Railway Signal Association, Digest of Proceedings, Vol.1, 1895-1905; Vol.2, 1905; Vol.3, 1906; Vol.4, 1907; Vol.5, 1908; Vol.6, 1909. Railway Signal Association, Journal, 1910, Vol.XIII; 1911, Vol.XIV; 1912,
Vol.XV; 1913, Vol.XVI; 1914, Vol.XVII; 1915, Vol.XVIII; 1916, Vol.XIX;1917, Vol.XX. Railway Signal Engineering, L. P. Lewis, London,1912. Railway Signaling, Pittsburgh, 1908. Railway Signaling in Theory and Practice, Latimer, Chicago, 1909. Railway Track and Track Work, Tratman, New York, 1908. Safe Railway Working, Stretton, 1886. Signal Engineer, The, 1908, Vol.1; 1909, Vol.2; 1910, Vol.3; 1911, Vol.4; 1912, Vol.5, 1913, Vol.6; 1914, Vol.7; 1915, Vol.8; 1916, Vol.9. Street Railway Road Bed, Pratt and Alden, New York, 1898.

LINES WITH OTHER CLASSES AND WITHIN THIS CLASS
MEANS PECULIAR TO SPECIAL TYPES OF RAILWAYS
Means peculiar to special types of railway, such as mono-rail, rack-rail, electric, pneumatic, logging, cash-carrier, elevated, cable, suspended, etc., and not of general utility or if claimed in connection with structure of such special types of railway will be found in the appropriate subclasses of other classes, for which see References to other Classes, below. But when such means are directed to the structure or operating mechanism of the switches of this class (246) subclass 415, they will be found in this class (246) subclass 419, indented thereunder.
SIGNALS AND INDICATORS IN OTHER CLASSES
For signals used for communication between occupants of a car or train see References to Other Classes, below.
For manually-set devices, such as train and engine signs, and markers capable of general use see references to Other Classes, below.
Where a semaphore is of the well known conventional railway type, (which is more fully described in the definition of subclass 479 of this class), the patent is classified here, but otherwise is some subclass of Class 116, Signals and Indicators, or Class 340, Communications: Electrical, unless claimed for railway use, in which case it is here classified.
SPEED CONTROL IN OTHER CLASSES
For speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway, see References to Other Classes, below.
TRAIN STOPPING IN OTHER CLASSES
For train stopping and control mechanism cooperating with obstacles fixed in position upon the track which have no moving parts see References to Other Classes, below.
Closures (gates) when performing a stopping rather than a signalling function will be found elsewhere, except that railway-gates and mine-doors actuated by the energy of a
moving vehicle or electrically controlled therefrom will be found in subclasses 125 and 292 of this class (246) and in the various subclasses indented thereunder.
TRACK STRUCTURE
For track structure other than as indicated above, see the Search Class references below.

REFERENCES TO OTHER CLASSES

SEE OR SEARCH CLASS:
14, Bridges, appropriate subclasses for track structure.
40, Card, Picture, or Sign Exhibiting, for manually-set devices, such as train and engine signs, and markers capable of general use
40, Card, Picture, or Sign Exhibiting, see the obstacle-operated, obstacle-controlled, and electrically-controlled subclasses of the changeable exhibitors for station, street and similar annunciators and card, picture and sign exhibitors not especially adapted for use as cab-signals, when placed in vehicles and actuated or controlled by obstacles or electrical contacts upon the track, except when there are claims upon the structure of the track-obstacle or intermittent electrical contact and no claims upon the structure of the annunciator or exhibitor in which case they are placed in this class (246).
49, Movable or Removable Closures, for Closures (gates) when performing a stopping rather than a signalling function.
91, Motors: Expansible Chamber Type, appropriate subclasses for speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway.
104, Railways, for train stopping and control mechanism cooperating with obstacles fixed in position upon the track which have no moving parts.
104, Railways, appropriate subclasses for means peculiar to special types of railway.
104, Railways, for track structure.
116, Signals and Indicators, for signals used for communication between occupants of a car or train.
116, Signals and Indicators, for manually-set devices, such as train and engine signs, and markers capable of general use
116, Signals and Indicators, subclasses 28+ and 200+, for hand actuated train-indicators or signals and indicators placed on moving trains or cars to indicate their motion or the speed or direction of their motion or which perform merely an identifying function, such as train or engine markers.
123, Internal-Combustion Engines, appropriate subclasses for speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway.
178, Telegraphy, for telegraph systems, note especially subclass 43 for space induction systems which are oftentimes used in train communication; (signals used for communication between occupants of a car or train)
180, Motor Vehicles, subclasses 167+ for a motor vehicle provided with means for controlling its operation which is responsive to electromagnetic radiation, magnetic force, or sound waves received from a source, or reflected from an object or surface, which is located apart from the vehicle; and subclasses 170+, for a motor vehicle provided with means which is responsive to the speed of the vehicle for maintaining its speed at, or preventing it from exceeding, a particular value.
180, Motor Vehicles, subclasses 170+, appropriate subclasses for speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway.
186, Merchandising, appropriate subclasses for means peculiar to special types of railway.
186, Merchandising, for train stopping and control mechanism cooperating with obstacles fixed in position upon the track which have no moving parts.
191, Electricity: Transmission to Vehicles, for the transmission of electricity to a moving vehicle, where no claims are made upon the apparatus actuated by the current or covering the uses to which the current is applied; subclasses 16-21 for circuit controllers actuated by the vehicle for the purpose of energizing sectionalized conductors used for supplying propulsion current thereto.
238, Railways: Surface Track, for track structure.
318, Electricity: Motive Power Systems, for speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway.
333, Wave Transmission Lines and Networks, note particularly subclasses 24+ for coupling networks which may be used in railway-signaling systems, and subclasses 1+ for
plural-channel systems including such coupling networks.
343, Communications: Radio Wave Antennas.
375, Pulse or Digital Communications, for pulse communication systems; (signals used for communication between occupants of a car or train)
379, Telephonic Communications, for telephone systems, note subclass 55 for space induction systems; (signals used for communication between occupants of a car or train) and Class
381, Electrical Audio Signal Processing Systems and Devices, especially subclasses 77+ and 86 for one-way electrical audio signal transmission systems for trains (signals used for communication between occupants of a car or train)
388, Electricity: Motor Control Systems, subclasses 800+ and 825+ for speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway.
414, Material or Article Handling, for train stopping and control mechanism cooperating with obstacles fixed in position upon the track which have no moving parts.
414, Material or Article Handling, appropriate subclasses for means peculiar to special types of railway.
418, Rotary Expansible Chamber Devices, appropriate subclasses for speed control vehicles, when all of the mechanism is upon the vehicle and there is no cooperation with devices on the track or roadway.
455, Telecommunications, for modulated carrier wave and light wave communications. (signals used for communication between occupants of a car or train)
701, Data Processing: Vehicles, Navigation, and Relative Location, subclasses 1+ for vehicle indication, operation, or guidance which requires a mathematical calculation. Note, where significant vehicle structure is recited, classification is in the appropriate vehicle class.

This subclass is indented under the class definition. Systems and devices not otherwise classifiable.

This subclass is indented under the class definition. Systems and devices specially adapted for the control of train movements by train-orders or by their equivalents transmitted from a central or directing station.

SEE OR SEARCH CLASS:
40, Card, Picture, or Sign Exhibiting, subclasses 541+ for number-display devices and similar markers displayed on trains to indicate car or train numbers or give other information useful to the train-dispatcher or other officials.
116, Signals and Indicators, subclass 30 for train-markers referred to above, and subclass 173 for flags used as train-markers and for supports for such flags.
178, Telegraphy, appropriate subclasses for miscellaneous electric telegraph systems.
258, Railway Mail Delivery, appropriate subclasses indented thereunder, for devices for delivering train-orders to moving trains.
340, Communications: Electrical, subclass 825.72 for radio remote control.
362, Illumination, subclass 253 and 459+ for signal and indicating lights carried by engines and cars, and 253, and 478+ for illuminated train and engine markers.
379, Telephonic Communications, appropriate subclasses for miscellaneous electric telephone systems.
455, Telecommunications, subclasses 500+ for miscellaneous radio systems comprising a plurality of transmitter and/or receiver means with a central control station.

This subclass is indented under subclass 2. Systems and devices in which the train-dispatcher can set or control the operation of railway-traffic-controlling devices from a distance.

SEE OR SEARCH THIS CLASS, SUBCLASS:
135 137, 141, 142, and 162, for indication that the signals, switches, etc., are properly actuated.

SEE OR SEARCH CLASS:
340, Communications: Electrical, subclass 298 for signal box systems having answer back or return call provision, and subclasses 313+ for miscellaneous signaling systems having answer back provision.
379, Telephonic Communications, subclass 418 for telephone-call systems having a return call indicator or answer back.

This subclass is indented under subclass 3. Systems having the signals given upon the engine cab or car or having mechanism which is actuated to stop the train or to control its motion.

SEE OR SEARCH THIS CLASS, SUBCLASS:
167 and the subclasses specified in the Notes thereto, for other systems within the class definition for a cab signal or train-control means.

This subclass is indented under subclass 3. Systems having means so that any one of a plurality of signals may be independently set or controlled from a distance, the number of line-wires used being less than the number of signals controlled.

SEE OR SEARCH THIS CLASS, SUBCLASS:
156 157, 164, 165, 424, 425, and 426, for selective mechanism and devices and all subclasses in the titles of which the words "Cab and control" appear, for means for actuating signals on trains.

SEE OR SEARCH CLASS:
178, Telegraphy, subclasses 23+ for printing telegraph systems.
250, Radiant Energy, subclasses 200+ and the classes specified in the Notes thereto for photo-sensitive electric systems for controlling a device.
307, Electrical Transmission or Interconnection Systems, subclasses 112+ for switching arrangements for distribution systems, particularly subclass 140 in which a remote switch is controlled by the exercise of control over the power current supplied to the switch.
335, Electricity: Magnetically Operated Switches, Magnets, and Electromagnets, subclasses 108+ for selective telephone-type switches of general utility.
340, Communications: Electrical, subclasses 825+ for selective signaling systems in which signals may be selectively controlled; and subclass 825.72 for radio-wave systems for controlling a device.
342, Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation), subclasses 73+ for miscellaneous systems for controlling a device by means of reflected or otherwise returned radio waves (radar).
370, Multiplex Communications, appropriate subclasses for multiplexing systems.
379, Telephonic Communications, subclasses 242+ for automatic telephone systems which usually involve selecting means; and subclasses 350+ for call transmitters for telephone systems.

This subclass is indented under subclass 2. Systems having devices placed upon the train to insure the observance of train orders.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and the subclasses specified in the Notes thereto, for details of cab signal or train-control mechanism.

This subclass is indented under subclass 2. Teles:graphic or telephonic systems specially adapted for communication between trains and the dispatcher or other stations.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab- signal systems giving only one or a limited number of indications.

SEE OR SEARCH CLASS:
375, Pulse or Digital Communications, for miscellaneous pulse communications.
455, Telecommunications, subclasses 500+ for miscellaneous analog modulated carrier wave communications.

This subclass is indented under subclass 7. Systems in which an inductive relation is established between the train and line, no physical connection being established.

SEE OR SEARCH THIS CLASS, SUBCLASS:
63 and 194, for inductive transmission of signals to moving trains.

SEE OR SEARCH CLASS:
178, Telegraphy, subclass 43 for inductive- telegraph systems.
191, Electricity: Transmission to Vehicles, subclass 10 for induction systems for transmitting electric power to a vehicle.
336, Inductor Devices, appropriate subclasses, for the structure of transformers and inductive reactors.
379, Telephonic Communications, subclass 55 for inductive telephone systems.

This subclass is indented under subclass 7. Systems in which a current is transmitted to or from the train by one or more continuous contacts with line conductors other than the traction rails, which may or may not be sectionalized.

SEE OR SEARCH THIS CLASS, SUBCLASS:
65 through 68, 73 and 86, all disclosing means for the transmission of signals to moving trains through electrical contacts continuously maintained.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+ for removing ice, snow and dirt from continuous and intermittent electric contacts.
191, Electricity: Transmission to Vehicles, for structure of the conductor and collector.

This subclass is indented under subclass 9. Systems in which a single continuous contact is used, current being returned by the traction rails.

SEE OR SEARCH THIS CLASS, SUBCLASS:
67 68, 71, 73, and 86, for system using the traction-rails or the return of the signal-current to the car, also the foregoing subclasses and in addition subclasses 65 and 66 for continuous- contact systems.

SEE OR SEARCH CLASS:
191, Electricity: Transmission to Vehicles, for structure of the conductor and the collector.

This subclass is indented under subclass 10. Systems in which two or more continuous contacts are used.
(1) Note. See the search note to subclass 10 for continuous-contact systems and also for systems disclosing the return of the current through the traction-rail.

SEE OR SEARCH CLASS:
191, Electricity: Transmission to Vehicles, for structure of the conductor and the collector.

This subclass is indented under subclass 9. Systems in which each train has its instruments cut constantly into the line in series with those of other trains or stations.

SEE OR SEARCH CLASS:
191, Electricity: Transmission to Vehicles, subclass 11 for structure of the conductor and the collector.

This subclass is indented under subclass 7. Emergency stations without operators, located along the permanent way between regular stations, at which trains may stop or be stopped for communication by telegraph or telephone with the dispatcher or other trains or stations or from which in an emergency signals may be controlled.

SEE OR SEARCH CLASS:
340, Communications: Electrical, subclasses 287+ for signal-box signaling systems.
379, Telephonic Communications, subclasses 56+ for portable telephone systems.
439, Electrical Connectors, for an electrical connector, per se, see especially subclasses 477+ for an electrical connector of the overhead line type having a handle, tool or manipulating means.

This subclass is indented under subclass 2. Day or night signals or combinations of same used for the purpose mentioned and usually adapted to be supported by or attached to the roof or outer wall of a station or signal cabin and provided with means for operating them from within the same.
(1) Note. This subclass also includes devices used at stations for holding train orders.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 473+ for signal structure.

SEE OR SEARCH CLASS:
40, Card, Picture, or Sign Exhibiting, subclass 462 for frames and clips for the holding and display of the train order.

This subclass is indented under subclass 14. Systems for insuring the proper display of the signal or the due delivery of the train order.

SEE OR SEARCH THIS CLASS, SUBCLASS:
6 for devices placed upon the train to insure the observance of train orders.

This subclass is indented under subclass 15. Devices for holding the train order, or train order blank, form part of the safety system.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 473+ for the signal structure.

SEE OR SEARCH CLASS:
24, Buckles, Buttons, Clasps, etc., appropriate subclasses, for the structure of clips for holding orders.
40, Card, Picture, or Sign Exhibiting, subclass 462 for frames and clips for the holding and display of the train orders.

This subclass is indented under subclass 14. Signals which rotate upon a vertical axis.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 473+ for signal structure.

This subclass is indented under subclass 14. Signals having two semaphore-arms which extend on opposite sides from a common support.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 479+ for semaphore structure.

This subclass is indented under the class definition. Systems in which the physical possession by an officer of the train of a train staff, ticket, tablet, or other token is a prerequisite to entrance upon the section or block.

SEE OR SEARCH THIS CLASS, SUBCLASS:
77 through 80 and 247, for train-counting mechanism.
133 134, 135, 141, 146, and 159, for details of electric locking and return-release indication.

This subclass is indented under the class definition. Systems in which a space interval is maintained between trains on the same track, usually by the subdivision of the way into definite sections termed "blocks", the movement of traffic being governed by cab or wayside signals or devices which control the brakes or motive power, or both.
(1) Note. Home signals indicate the presence or absence of trains within the block about to be entered. Distant signals (usually semaphores having notched blades) indicate the condition of adjacent or distant blocks other than the block about to be entered. The combined functions of the home and
distant signals are sometimes performed by a three-position signal, indicating by its three positions, respectively, the presence of a train in the block ahead, the second block ahead, or that both blocks are clear.

SEE OR SEARCH THIS CLASS, SUBCLASS:
19 for systems closely related in function where the physical possession by an officer of the train of a staff ticket or other token is a prerequisite to entrance upon the block.

This subclass is indented under subclass 20. Systems in which the train automatically cooperates with human agency in the actuation or control of the elements of the system.
(1) Note. These systems are sometimes called "controlled Manual". The electric control by trains of manually- actuated signals or vice versa is an example of such cooperation.

SEE OR SEARCH THIS CLASS, SUBCLASS:
105 106, 112, 160, 164, 165, and 183, for manual-control features.

This subclass is indented under subclass 21. Systems in which the train uses electrical means in performing its automatic function.
(1) Note. This subclass includes the so-called "controlled-manual-block" systems.

SEE OR SEARCH THIS CLASS, SUBCLASS:
105 106, 112, 160, 164, 165, and 183, for manual-control features.

This subclass is indented under subclass 22. Systems in which
means are provided for actuating audible or visual signals upon the cab or train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 22. Systems in which use is made of train-actuated circuit controllers.

SEE OR SEARCH THIS CLASS, SUBCLASS:
72 through 80, 82-84, 88, 90, 91, 126, 127, 246-252 and 259, for train-actuated circuit-closers. See also search mote to subclass 246.

This subclass is indented under subclass 22. Systems in which the signal clearing operations require the cooperation of the operators at each end of the block and also the absence of trains from the block, which when present, by electrical means, render it impossible to clear the signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 and 106, for manually-controlled block signaling systems of the lock and block type.
subclasses 131+ and the subclasses specified in the Notes thereto, for details of locking and interlocking, and switching, signaling, and similar systems.

This subclass is indented under subclass 25. Systems in which track circuits are used for controlling the devices of the
system.

SEE OR SEARCH THIS CLASS, SUBCLASS:
34 41, 58, 95, and 98, for block-signaling systems having specific track circuits.
subclasses 128+ and 130, for automatic-highway signal systems, mine door and/or gate systems having specific track circuits.

This subclass is indented under subclass 20. Systems having train-control devices which operate automatically without direct human intervention.

SEE OR SEARCH THIS CLASS, SUBCLASS:
21 and appropriate indented subclasses for automatic systems in combination with manually-actuated signals.

This subclass is indented under subclass 27. Systems in which the traffic- controlling devices are actuated and controlled only by electrical means.
(1) Note. The means employed upon the train for operating cab signal and train-control mechanism may by of any type--e.g., electrical, fluid-pressure, mechanical, etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:
22 for semi-automatic block signaling systems in which electrical means are used for performing the automatic function.
subclasses 114+ for automatic grade-crossing protection systems having electrical means for operating the protecting means.

SEE OR SEARCH CLASS:
104, Railways, subclass 238 for vehicle propulsion control
by block system wherein a peculiar type of guideway is claimed (e.g., cable, model, overhead, etc.).

This subclass is indented under subclass 28. Systems in which the traffic- control devices are actuated and controlled by waves of radiant energy as heat, light, etc.

SEE OR SEARCH CLASS:
359, Optics: Systems (Including Communication) and Elements, subclasses 109+ for signalling systems in which intelligence is transmitted over a light or analogous beam.
455, Telecommunications, subclass 200.1 and the classes and subclasses specified in the Notes thereto for photocell-controlled electric circuits and photocell apparatus.

This subclass is indented under subclass 29. Systems in which the signals or automatic-stop devices are actuated or controlled by the methods of so-called "wireless telegraphy", making use of Hertzian waves.

SEE OR SEARCH CLASS:
340, Communications: Electrical, subclass 825.69 and 825.72 for radio-wave systems for controlling a device.
342, Communications: Directive Radio Wave Systems and Devices (e.g., Radar, Radio Navigation), appropriate subclasses for miscellaneous radio-signaling and teledynamic systems, particularly subclasses 61+ for the miscellaneous systems for controlling a device by means of reflected or otherwise returned radio wave energy; See the classes under "SEARCH CLASS" in the class definitions of Class 343 for the other classes which provide for radiant-energy systems for controlling a device.

This subclass is indented under subclass 28. Systems in which
means not on the car or train are provided whereby under conditions of danger the supply of propulsion current is cut off or is so reduced that the car is stopped or its speed controlled. (1) Note. The control of the supply of propulsion current is most cases will be by other cars or trains which constitute a hazard to the controlled car or train.

SEE OR SEARCH THIS CLASS, SUBCLASS:
187 and the subclasses specified in the Notes thereto, for train-control devices located on the train whereby the motor of an electric car is deprived of propulsion current.

SEE OR SEARCH CLASS:
104, Railways, subclass 238 for vehicle propulsion control by block system wherein a peculiar type of guideway is claimed (e.g., cable, model, overhead, etc.).
191, Electricity: Transmission to Vehicles, subclasses 16-21 for conductor-supply systems for railways wherein the conductor is provided with a plurality of sections, one or more of the sections being manually de-energized and the system having means for connecting the de-energized section to the supply feeder.

This subclass is indented under subclass 31. Systems in which the flow of propulsion current to one car or train under conditions of danger controls the flow to other cars or trains.

This subclass is indented under subclass 28. Systems in which signals are so arranged as to give danger or caution indications to trains running in both directions on the same track.
(1) Note. The so-called "A. P. B." or absolute-permissive block systems are here included.
(2) Note. Only systems controlled by track-circuits are here included.

This subclass is indented under subclass 28. Systems in which an alternating or pulsating current used for actuating or controlling the traffic controlling devices and derived from a source not on the train uses both traction rails as conductors in series for the major portion of the block.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
176 and 253, for switch or signal actuated circuit-breakers in track-circuits.
449 450 and 451, for tie-bars with insulated joints.

SEE OR SEARCH CLASS:
238, Railways: Surface Track, subclass 164 for the structure of rail bonds and subclass 152 for insulated rail joints.

This subclass is indented under subclass 34. Systems in which super-imposed propulsion current, either direct or alternating, is returned through one of the traction rails which is not sectionalized.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
34 38, 39, and 40, for alternating track-circuits showing one unbroken traction-rail, its use for return of propulsion-current not being specified.
42 43 and 61, for the use of propulsion-current in other systems.

This subclass is indented under subclass 35. Systems in which both traction rails are used for the return of the
super-imposed propulsion current, neither rail being sectionalized.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
35 and 37, for superposition of propulsion-current on an alternating or varying track-circuit current.
42 43 and 61, for the superposition of propulsion-current on a direct track-circuit current.

This subclass is indented under subclass 36. Systems in which one or both of the traction-rails are divided into sections by insulated joints, the rails being made continuous for the return of the super-imposed direct propulsion-current by inductance-bonds or similar devices, which by impedance prevent the passage of the alternating signal-circuit.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
35 and 36, for the superposition of propulsion-current upon alternating track-circuit currents.
42 43 and 61, for the superposition of propulsion-current upon direct track-circuit currents.

This subclass is indented under subclass 34. Systems in which the home indication is actuated or controlled by the presence or absence of current and the distant indication by the change of some characteristic of the track-circuit current.
(1) Note. As line-wire distant control is dispensed with, the system is sometimes referred to in the art as "wireless", but should not be confused with the true or Hertzian-wave "wireless" of subclass 30.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit
systems.
35 44, 45, and 60, for means for the actuation of the signals.
52 224 and 481, for home and distant type.
53 and 223, for three-position type of semaphore.

SEE OR SEARCH CLASS:
335, Electricity: Magnetically Operated Switches, Magnets, and Electromagnets, subclasses 230+ for polarized electromagnets and subclasses 266+ for differential electromagnets.
340, Communications: Electrical, subclasses 825+ for selective signaling systems of general application.

This subclass is indented under subclass 34. Systems in which one or more line-wires extending back for at least the entire length of the block are used for controlling or actuating the distant signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
subclasses 46+ and 60, for line-wire control systems.
52 and 224, for the structure of or means for the actuation of the signals.
53 and 223, for three-position type of semaphore.
52 224 and 481, for home and distant type.

This subclass is indented under subclass 34. Systems in which the blocks are independent, trains only controlling the devices at the entrance of the blocks in which they are running.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128, and 130, for track-circuit systems.
54 and the appropriate indented subclasses for single-block systems.

This subclass is indented under subclass 28. Systems in which a direct, normally closed, continuous current, either actuating or controlling traffic-controlling devices and derived from a source not on the train, uses both traction-rails in series as conductors for the major portion of the block.
(1) Note. This type is known to the Railway Signal Association by the title "D.C. automatic block".

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
70 for cab signal or train-control systems similar to that in this subclass.
130 for highway signals, gates, and doors actuated or controlled through closed track-circuits.
160 for switch-locks controlled by electric track-circuits.
253 for devices for breaking the continuity of the circuit when a switch is misplaced or a signal goes to danger.
449 450 and 451, for tie-bars with insulated joints.

SEE OR SEARCH CLASS:
238, Railways: Surface Track, subclass 164 for the structure of rail-bonds and subclass 152 for insulated rail-joints.

This subclass is indented under subclass 41. Systems in which a direct propulsion-current is returned by and super-imposed upon one or both of the track-rails in which the signal
controlling current flows.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
subclasses 35+ 43 and 61, for superimposed propulsion-current.

This subclass is indented under subclass 42. Systems in which the super-imposed propulsion-current is either alternating or pulsating.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
subclasses 35+ and 61, for superimposed propulsion-current.

This subclass is indented under subclass 41. Systems in which the distant signal is controlled by the change of some characteristic of the track-circuit current.
(1) Note. As the use of external line-wires is dispensed with, the system has long been known in the art as "wireless", although not wireless in the sense of the teles:graphic art or of subclass 30 of this class.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+ 95, 98, 128+, and 130, for track-circuit systems.
38 50 and 60, for wireless systems.

SEE OR SEARCH CLASS:
340, Communications: Electrical, subclasses 825+ for
selective-signaling systems of general application.

This subclass is indented under subclass 44. Systems in which a reversal of the direction of current flow is used for controlling the distant signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
38 50 and 60, for wireless systems.

This subclass is indented under subclass 41. Systems in which one or more line wires extending back the entire length of the block are used for controlling or actuating the distant signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
39 47 to 53 and 60, for line-wire systems of control.

This subclass is indented under subclass 46. Systems in which means are provided for actuating traffic-controlling devices placed upon the train or car.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
39 46, 48 to 53 and 60, for line-wire systems of control.
subclasses 167+ and all subclasses noted in the search
notes appended thereto, for details relating to the control of signals placed upon a moving car or train or to the control of its motion.

This subclass is indented under subclass 47. Systems in which an electric circuit on the train, normally closed through the track-rails, is broken by the passage of the train over one or more insulated rail-joints when a condition of danger exists, the break in the rails being electrically bridged under conditions of safety.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
39 46, 49 to 53 and 60, for line-wire systems of control.
57 75 and 179, for bridged-insulated-rail-joint systems.
subclasses 167+ and all subclasses noted in the search Notes appended thereto, for cab and control features.

This subclass is indented under subclass 47. Systems in which an electric current is transmitted from the track into the cab or a local cab-circuit is closed by means of so-called "ramp rails" or intermittent contact plates or rails.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
39 46, 48 to 53, and 60, for line-wire systems of control.
56 69+, 74, 85, 92, 195, 229, and 233+, for other systems characterized by an intermittent contact similar to that in this subclass.
subclasses 167+ and all subclasses noted in the search notes appended thereto, for cab and control features.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+ for devices for cleaning ice, snow, and dirt from continuous and intermittent electrical contacts.

This subclass is indented under subclass 46. Systems in which the distant signal is actuated or controlled by changes in the direction of current-flow or in some other characteristic or the current in a circuit other than the track-circuit.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
38 44, 45 and 60, for current characteristic control.
39 46 and 60+, for line-wire systems of control.

This subclass is indented under subclass 46. Systems in which the signal at the entrance to any block is retained in its danger position until after a train has entered the next block ahead and has proceeded therein a certain predetermined distance.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
39 46 to 50, 52, 53, and 60, for line-wire systems of control.

This subclass is indented under subclass 46. Systems in which two signals, "home" and "distant" so called, usually having a common support, are placed at the entrance to each block and respectively indicate the condition of the block about to be
entered and or the next block ahead.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 128+, and 130, for track-circuit systems.
33 38, 39, 44+, 51, 224, and 481, for motors for actuating home and distant signals.
39 46+, 53 and 60, for line-wire systems of control.

This subclass is indented under subclass 46. Systems in which a so-called "three-position signal" is placed at the entrance to each block and indicates by its three different aspects the occupancy of the first or second blocks ahead or that both blocks are clear.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
33 38, 39, 44, 45, 51, 223, and 479, for detail of three-position signal mechanism.
39 46 to 52, and 60, for other methods of line-wire distant control.

This subclass is indented under subclass 41. Systems in which the blocks are independent, trains only controlling the devices of the blocks in which they are running.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
40 for single-block systems.

This subclass is indented under subclass 54. Systems in which the traffic-controlling devices are placed upon the car or train.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
40 for single-block systems.
subclasses 167+ and all subclasses referred to in the search notes appended thereto, for details of the cab and control mechanism.

This subclass is indented under subclass 55. Systems in which intermittent contacts or so-called "ramp-rails" are used for establishing electrical connection with the moving train.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+ 95, 98, 128+, and 130, for track-circuit systems.
40 for single-block systems.
49 69, 70, 71, 74, and 195, for intermittent contacts controlling cab-signals and train movements.
85 and 92, for such contacts used with other types of block systems.
subclasses 167+ and all subclasses given in the search notes appended thereto, for cab and control features.
229 233, 234, and 235, for intermittent contacts in motor systems.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+ for devices for cleaning ice, snow, and dirt from continuous and intermittent electrical contacts.

This subclass is indented under subclass 55. Systems in which an electric circuit upon the train, normally closed through the track rail or rails, is broken by the passage of the car over one or move insulated rail-joints, the break in the rails being electrically closed under conditions of safety.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
40 for single-block systems.
48 75 and 179, for bridged-insulated-rail-joint systems.
subclasses 167+ and all subclasses given in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 28. Systems in which a direct continuous current used for actuating and controlling traffic-controlling devices, normally open and derived from a source not on the train, uses both traction-rails in series as conductors in opposite directions for the major portion of the block.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 95, 98, 128+, and 130, for track-circuit systems.
449 450 and 451, for tie-bars with insulated joints.

SEE OR SEARCH CLASS:
238, Railways: Surface Track, subclass 14.1, for the structure of rail-bonds and subclass 152, for insulated rail-joints.

This subclass is indented under subclass 58. Means are
provided for actuating audible or visual signals upon the cab or train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 7+ for the transmission of teles:graphic and telephonic communications to and from moving cars.
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 58. Means are provided for the control of distant or three-position signals or for the control of a single signal from a plurality of blocks.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 95, 98, 128+, and 130, for track-circuit systems.
subclasses 35+ 38, 39, 44+, and 46+, for systems of distant-signal control.

This subclass is indented under subclass 28. Propulsion-current is superimposed upon the current controlling the signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+ 95, 98, 128+, and 130, for track-circuit systems.
35 36, 37, 42, and 43, for propulsion-current superimposed upon track-circuits.

This subclass is indented under subclass 28. Systems in which means are provided for actuating traffic-control devices upon the cab or train.
(1) Note. The use of fluid-pressure means upon the cab or train for operating or controlling brake and throttle valves or electrical controllers or for operating brakes and audible or visual signals is not considered as combined fluid-pressure and electric in the sense of subclass 93, and therefore systems using such means have been herein included.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 7+ for systems which disclose or claim means for the teles:graphic or telephonic transmission of written matter or speech.
31 for automatic-stop systems in which electrical propulsion-current is cut out from trolly-wire or third-rail sections.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 62. Systems in which an inductive relation is established between the train and the line, no physical connection being maintained between them.

SEE OR SEARCH THIS CLASS, SUBCLASS:
8 and 194, for inductive systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

SEE OR SEARCH CLASS:
336, Inductor Devices, appropriate subclasses for the structure of transformers and inductive reactors.

This subclass is indented under subclass 62. Systems in which the source of current is a battery or dynamo placed upon the train.
(1) Note. Systems in which train-batteries actuate local train-circuits or supply current used for purposes other than signal actuation or control are not here included, but will be found in the appropriate line-battery classes.

SEE OR SEARCH THIS CLASS, SUBCLASS:
86 for train-battery systems from which the cab and control feature is absent.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+, for devices for cleaning ice, snow and dirt from continuous and intermittent electrical contacts.
307, Electrical Transmission or Interconnection Systems, subclass 9.1 for electrical systems mounted on a vehicle.
322, Electricity: Single Generator Systems, appropriate subclasses, for miscellaneous single-generator systems. See subclass 1 for portably mounted single-generator systems.

This subclass is indented under subclass 64. Systems in which continuous contacts are maintained by shoes, brushes, and their equivalents between two or more metallic conductors extending parallel to the track. The traction-rails may or may not form part of the circuit.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 9+ 66-68, 73, and 86, for continuous- contact systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab control and features.

SEE OR SEARCH CLASS:
191, Electricity: Transmission to Vehicles, appropriate subclasses, for details of the electric conductors and collectors.

This subclass is indented under subclass 65. Systems in which the continuous-contact rails, the traction-rails, or both, are divided into sections or blocks insulated from each other.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 9+ 65, 67, 68, 73, and 86, for continuous- contact systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 64. Systems in which a single continuous contact is maintained by shoes, brushes, or other equivalents between the moving vehicle and a metallic conductor extending parallel with the track.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 9+ 65, 66, 68, 73, and 86, for continuous- contact systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

SEE OR SEARCH CLASS:
191, Electricity: Transmission to Vehicles, appropriate subclasses, for details of the electric conductors and collectors.

This subclass is indented under subclass 67. Systems in which the conductor, the traction-rails, or both, are divided into sections or blocks insulated from each other.

SEE OR SEARCH THIS CLASS, SUBCLASS:
10 and 71, for traction-rail return.
66 for two or more independent single-continuous-contact-sectional systems upon the same train, the same being, in effect, mere duplications of systems otherwise properly classifiable in this subclass.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 64. Systems in which the train-current passes out by or returns through the medium of one or more intermittent contacts or "ramp-rails", so-called.

SEE OR SEARCH THIS CLASS, SUBCLASS:
49 56, 70, 71, 74, 85, 92, 122, 195, 229, 233, 234, and 235, for intermittent- contact systems from which cab and control features are absent.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 69. Systems in which the traction-rails form part of the circuit, the current passing through them in both directions.

SEE OR SEARCH THIS CLASS, SUBCLASS:
49 56, 69, 74, 85, 92, 122, 195, 229, 233, 234, and 235, for intermittent-contact systems from which cab and control features are absent.

This subclass is indented under subclass 69. Systems in which the traction-rails form part of the circuit, the current passing through them in one direction only.

SEE OR SEARCH THIS CLASS, SUBCLASS:
49 56, 69, 70, 85, 92, 122, 195, 229, 233, 234, and 235, for intermittent-contact systems from which cab and control features are absent.

This subclass is indented under subclass 62. Systems in which the electrical energy is derived from the propulsion-current.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 81+ for propulsion-current signaling.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 62. Systems in which the current is conducted from the track through the cab or car by means of a continuous contact maintained with one or more line conductors, not traction-rails, for the major portion of the block.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 9+ 65+, 67+, and 87, for continuous-contact systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+, for devices for cleaning ice, snow, and dirt from continuous and intermittent electrical contacts.
191, Electricity: Transmission to Vehicles, appropriate subclasses, for details of the electric conductors and collectors.

This subclass is indented under subclass 62. Systems in which the current is conducted from the track through the cab or car by means of intermittent contacts, periodically established, with contact-plates, ramp-rails, or similar devices other than traction-rails.

SEE OR SEARCH THIS CLASS, SUBCLASS:
56 69, 70, 71, 85, 92, 195, 229, 233, 234, and 235, for systems with intermittent contacts from which cab signal and train-control features are absent.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+ for devices for cleaning ice, snow and dirt from continuous and intermittent electrical contacts.

This subclass is indented under subclass 62. Systems in which an electrical circuit upon the train, normally closed through the track rail or rails, is broken by the passage of the car over one or more insulated rail-joints, the break in the rails being electrically closed under conditions of safety.

SEE OR SEARCH THIS CLASS, SUBCLASS:
48 57 and 179, for systems disclosing bridged-insulated rail-joints or analogous features.

This subclass is indented under subclass 62. Systems includes electrically-actuated track-detents or obstacles mechanically actuate mechanism on moving trains, such as brake-valves, levers, circuit-closers, etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for track-detents used in various systems of block, frequently for actuating the cab and control mechanism.
subclasses 201+ for the structure of the track-detent.

This subclass is indented under subclass 28. Counting and cancelling mechanism, usually of the step-by-step variety, is provided, whereby as many trains or car-wheels as enter must leave the block before the signal can be restored to safety.

SEE OR SEARCH THIS CLASS, SUBCLASS:
19 72, 81, and 247, for systems using propulsion-current, but lacking counting and canceling devices.
19 78+ and 247, for counting mechanism.
subclasses 246+ and subclasses mentioned in the search notes appended thereto, for various types of circuit-controllers.

This subclass is indented under subclass 77. Subject matter having ratchet-wheels which are actuated and controlled by pawls or escapements.

SEE OR SEARCH THIS CLASS, SUBCLASS:
19 72, 77+, and 247, for details of the counting and canceling devices.

This subclass is indented under subclass 78. Subject matter having a single ratchet-wheel which is actuated by two opposed pawls moving in the same plane and tending to turn it in opposite directions.

SEE OR SEARCH THIS CLASS, SUBCLASS:
19 72, 77+, and 247, for details of the counting and canceling devices.

This subclass is indented under subclass 79. Subject matter having two ratchet-wheels which are placed in parallel on the same arbor or a single wheel having two sets of teeth in parallel is actuated by opposed pawls to produce rotation in opposite directions.

SEE OR SEARCH THIS CLASS, SUBCLASS:
19 72, 77+, and 247, for details of the counting and canceling devices.

This subclass is indented under subclass 28. Subject matter having the propulsion-current used to actuate or control the signals of the block.

SEE OR SEARCH THIS CLASS, SUBCLASS:
72 for propulsion-current signaling.

This subclass is indented under subclass 81. Subject matter having one or more circuit-controllers continuously rotated in one direction, which are actuated either electrically or mechanically, but which do not perform a counting and canceling function.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 246+ and the subclasses mentioned in the search notes appended thereto for various types of circuit-controllers.

This subclass is indented under subclass 81. Subject matter in which circuit-controllers are provided which are mechanically actuated by the moving car.

SEE OR SEARCH THIS CLASS, SUBCLASS:
72 77, and appropriate indented subclasses, and 81, for systems making use of propulsion-current.
subclasses 246+ and the subclasses mentioned in the search notes appended thereto, for the structure of the controller.

This subclass is indented under subclass 83. Subject matter having circuit-controllers actuated by the trolley-arm plow or other current-collector.

SEE OR SEARCH THIS CLASS, SUBCLASS:
72 77, and appropriate indented subclasses, and 81, for systems making use of propulsion-current.

This subclass is indented under subclass 81. Subject matter having traffic-controlling devices actuated or controlled by circuits closed through intermittent contacts established between the moving vehicle and stationary conductors.

SEE OR SEARCH THIS CLASS, SUBCLASS:
56 69, 74, 92, and 195, for systems using intermittent contacts.
subclasses 77+ for systems making use of the propulsion-current.
229 233, 234+, 254, and 255, for structure of such contacts.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+, for devices for cleaning ice, snow, and dirt from continuous and intermittent electrical contacts.

This subclass is indented under subclass 28. Systems in which the source of the current is carried upon the train.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 9+ 65, 68, and 73, for continuous-contact systems.
subclasses 64+ for train-current-supply systems.

This subclass is indented under subclass 28. Systems in which the source of the current is not carried on the train.

This subclass is indented under subclass 87. Systems in which a plurality of signals, usually electric lamps, are displayed within the block.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 246+ and the subclasses mentioned in the search notes appended thereto, for various types of circuit-controllers.

This subclass is indented under subclass 87. Systems in which the circuit for actuating or controlling the signals is opened of closed by car-wheels bridging two short parallel insulated track-sections.

SEE OR SEARCH THIS CLASS, SUBCLASS:
129 for short-sectional-rail-closure systems.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+, for devices for cleaning ice, snow and dirt from continuous and intermittent electrical contacts.

This subclass is indented under subclass 87. Systems in which the circuit for actuating or controlling the signals is opened or closed by controllers actuated by the energy of the moving train.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 246+ and the subclasses mentioned in the search notes appended thereto, for various types of circuit-controllers.

This subclass is indented under subclass 90. Systems in which the car-actuated controllers governs the action of one or more controllers of other circuits, which perform the function of a relay.

This subclass is indented under subclass 87. Systems in which the circuit is closed by devices carried by the train, which make electrical connection with short rails, contact-plates, etc.

SEE OR SEARCH THIS CLASS, SUBCLASS:
49 56, 69, 70, 71, 74, 85, 195, 229, 233, 234, 235, and 254, for intermittent- contact systems.

SEE OR SEARCH CLASS:
104, Railways, subclasses 279+, for devices for cleaning ice, snow and dirt from continuous and intermittent electrical contacts.

This subclass is indented under subclass 27. Subject matter having electrical and fluid-pressure means used in combination for the actuation and control of roadway-signals, track-detents, contacts, and similar devices, irrespective of the means employed upon the train for actuating the cab and
control mechanism.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 140+ for interlocking mechanism actuated by electric fluid-pressure means.
subclasses 257+ and the subclasses mentioned in the search notes appended thereto, for fluid-pressure-motor structure.
258 and 259, for electric fluid-pressure motors for actuating switches and signals generally.

This subclass is indented under subclass 93. Subject matter in which means are provided for actuating signals upon the train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
140 and 141, for interlocking mechanism actuated by electric fluid-pressure means.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.
subclasses 257+ and all subclasses mentioned in the search notes appended thereto, for fluid-pressure-motor structure.
258 and 259, for electric fluid-pressure motors for actuating switches and signals generally.

This subclass is indented under subclass 93. Systems which are controlled through track-circuits.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 70, 94, 98, 128, 129, and 130, for
track-circuit control.
subclasses 257+ and all subclasses mentioned in the search notes appended thereto, for fluid-pressure-motor structure.

This subclass is indented under subclass 27. Subject matter having electrical and mechanical means used in combination for the actuation and control of roadway-signals, detents, and other track devices, irrespective of any means employed upon the train for actuating cab and control mechanism. The mechanical means may or may not utilize the energy of the moving vehicle.

SEE OR SEARCH THIS CLASS, SUBCLASS:
97 through 99 and 263, for electromechanical systems.
102 103 and 262, for mechanical-motor systems.

This subclass is indented under subclass 96. Subject matter having means provided for actuating audible or visible signals upon the car or train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
96 98, 99, and 263, for electromechanical systems.
102 103 and 262, for mechanical-motor systems.
subclasses 167+ and subclasses specified in the notes thereto for cab and control features.

This subclass is indented under subclass 96. Subject matter having track circuits to control the traffic-controlling
devices.

SEE OR SEARCH THIS CLASS, SUBCLASS:
26 34+, 41+, 58+, 70, 95, 128, 129, 130, and 160, for the control of signals through track-circuits.
subclasses 96+ and 263, for the electromechanical actuation of signals.
102 103 and 262, for mechanical-motor systems.

This subclass is indented under subclass 96. Subject matter having clockwork or similar trains of gearing which are made use of and are provided with electrically-actuated escapement or latch-release devices.

SEE OR SEARCH THIS CLASS, SUBCLASS:
96 97, 98, and 263, for mechanical switch and signal motors electrically controlled.
102 103 and 262, for mechanical-motor systems.
110 and 262+, for signals actuated by clockwork.

This subclass is indented under subclass 27. Subject matter having fluid-pressure means used for actuating and controlling roadway-signals, detents, and other track devices, irrespective of the means employed upon the train for actuating the cab and control mechanism.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 93+ 116, 139, 142, 257+, and 361, for fluid-pressure actuation of signals.
140 141, 258, and 259, for electrically-controlled, for fluid pressure actuation of signals.
257 see search notes appended thereto, for fluid-pressure
structure.

This subclass is indented under subclass 100. Subject matter having means provided for actuating audible or visible signals upon the cab or train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.
subclasses 257+ and all subclasses mentioned in the search notes appended thereto, for fluid-pressure-motor structure.

This subclass is indented under subclass 27. Subject matter having roadway-signals, detents, and other track devices actuated and controlled solely by mechanical means, usually involving direct contact with the moving train or some device attached thereto, and irrespective of the means employed upon the train, if any, for actuating the cab and control mechanism.

SEE OR SEARCH THIS CLASS, SUBCLASS:
110 113 and 262, for mechanical systems.
subclasses 201+ for the track-detent.

This subclass is indented under subclass 102. Subject matter having means provided for actuating audible or visible signals upon the cab or train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 102+ and all subclasses mentioned in the search notes appended thereto, for mechanical-motor systems.
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 20. Subject matter having traffic-controlling devices actuated either by manual power or by manually-controlled power mechanism.
(1) Note. So-called "manual-block systems" are here included.

SEE OR SEARCH THIS CLASS, SUBCLASS:
21 and appropriate indented subclasses, for systems of manual actuation in combination with automatic signals.
112 and 117, for manual systems at grade-crossing.
118 and 119, for manual systems at draw-bridges.
143 through 158, for manual systems of interlocking.

This subclass is indented under subclass 104. Subject matter having signals either actuated or controlled by electric means or having electricity used for performing some function other than transmitting telephonic or code messages to the signalmen.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 22+ for electromanual systems automatically controlled by the trains or cars.
104 for systems which are otherwise manual and which use
electrical means for the purposes of communication between signalmen in cabins. Also see search notes appended thereto.

This subclass is indented under subclass 105. Subject matter having a signal which cannot be cleared at one end of the block until it has been electrically unlocked by the operator at the other end.
(1) Note. The so-called "manual lock and block systems" are here included.

SEE OR SEARCH THIS CLASS, SUBCLASS:
25 26 and 131+, for locking features.

Subject matter under subclasss 20 having devices which are used for permanently recording the movements of trains, signals, or other movable units or indicating the disregard of signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:
123 and 185, for recording systems.

SEE OR SEARCH CLASS:
346, Recorders, appropriate subclasses for recorder structure.

This subclass is indented under the class definition. Systems and devices which include means for giving a time indication concerning trains which have previously passed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
109 110 and 123, for time-indication systems.

This subclass is indented under subclass 108. Systems and devices in which the retarded flow of gases, liquids, or finely-divided particles of solids is utilized for giving the time indication.

This subclass is indented under subclass 108. Systems and devices in which a visual indicator set by the last train which passed is suddenly obscured or reset at the expiration of a predetermined time-limit.

SEE OR SEARCH THIS CLASS, SUBCLASS:
96 98, 102, 108, 109, 248, and 262, for systems and devices more or less analogous.

This subclass is indented under the class definition. Systems and devices which include any arrangement of train-controlling means--such as signals, derails, interlocking, automatic stops, etc., --designed to prevent collisions where two or more lines of railway cross at grade.

SEE OR SEARCH THIS CLASS, SUBCLASS:
118 for similar systems used at drawbridges.
125 260, 293, and 473, and appropriate indented subclasses for signal structure.
465 and the subclasses indicated in the search notes appended thereto, for the structure of the crossing.

This subclass is indented under subclass 111. Subject matter in which the train automatically cooperates with human agency in the actuation or control of the traffic devices.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 21+ for semi-automatic block-signaling systems.
111 125, 260, 293, and 473, and appropriate indented subclasses for signal structure.

This subclass is indented under subclass 111. Subject matter having means actuated or controlled automatically by the approaching train and without the intervention of human agency.

SEE OR SEARCH THIS CLASS, SUBCLASS:
21 27 and 125+, which have automatic actuation or control of the type required, for systems of automatic actuation and control.
111 125, 260, 293, and 473, and appropriate indented subclasses for signal structure.
118 for drawbridge protection is general.

This subclass is indented under subclass 113. Subject matter having electric means for the actuation or control of the traffic-controlling devices.

SEE OR SEARCH THIS CLASS, SUBCLASS:
111 125, 260, 293, and 473, and appropriate indented subclasses, for signal structure.

This subclass is indented under subclass 114. Subject matter having means provided for giving indications upon the train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under subclass 113. Subject matter having fluid-pressure means for the actuation or control of the signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:
93 100, 101, 139, 142, 257, 271, 272, and 361, for systems using fluid-pressure means.
111 125, 260, 293, and 473, and appropriate indented subclasses, for signal structure.

This subclass is indented under subclass 111. Subject matter having means provided for actuating audible or visual signals upon the cab or train or for stopping it or controlling its speed.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under the class definition. System of train-controlling means designed to prevent trains and cars from running into an open drawbridge.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 111+ for analogous systems of grade crossing
protection.
125 260, 293, and 473, and appropriate indented subclasses for signal structure.

SEE OR SEARCH CLASS:
14, Bridges, subclass 30, 41, 46, 55, 57, 59, 61, 63, 65, 67, and 69, for bridges having movable parts such as drawbridges and having locking devices and 49 and 50+ for gates and signals operated or controlled by the opening of the bridge.

This subclass is indented under subclass 118. Subject matter having means provided for actuating signals on approaching trains or for stopping them or controlling their motion.

SEE OR SEARCH THIS CLASS, SUBCLASS:
subclasses 167+ and all subclasses mentioned in the search notes appended thereto, for cab and control features.

This subclass is indented under the class definition. Subject matter having signals, indicators, and train-controlling devices which are automatically set at "danger" by the occurrence of any defect in the permanent way, including bridges.

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subclasses 111+ 118 and 220, for analogous systems.

This subclass is indented under subclass 120. Subject matter having roadway-defect signals which are actuated or controlled by electrical means.

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subclasses 246+ and appropriate subclasses mentioned in the search notes appended thereto, for structure of the circuit-controllers.
subclasses 473+ and appropriate subclasses mentioned in the search notes appended thereto, for signal structure.

This subclass is indented under the class definition. Systems and devices in which the train automatically indicates its position upon the line as by lights, indicators, moving diagrams, etc.

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116, Signals and Indicators, appropriate subclasses for miscellaneous nonelectrical signals.
235, Registers, appropriate subclasses for registering apparatus and systems.

This subclass is indented under subclass 122. Systems in which a permanent record is automatically made at a distant station of the time at which a train passes a given point.

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4 5 and 108+, for automatic-signal or time indication.

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346, Recorders, appropriate subclass.

This subclass is indented under subclass 122. Systems in
which an audible or visual indication is given, usually in a tower or station, of the approach of a train, and in some cases also of its number, its intended route, or other necessary information.

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107 162 and 220, for switch and block-system signal indicators or recorders.

This subclass is indented under the class definition. Systems in which highway-crossing signals, gates, and mine-doors are actuated or controlled from the moving train or vehicle by electrical means.

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111 260, 293, and 473, and appropriate indented subclasses for signal structure.
221 and the appropriate indented subclasses, for the electric actuation of switches and signals other than those used at highway-crossing.
subclasses 246+ and all subclasses mentioned in the search notes appended thereto, for various types of circuit-controllers.
261 and 272, for gate structure.

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49, Movable or Removable Closures, appropriate subclasses, for closures (gates) and closure-actuating mechanism.

This subclass is indented under subclass 125. Subject matter having car-actuated circuit-controllers located on the right of way.

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246 and the subclasses specified in the Notes thereto for various types of circuit-controllers.
subclasses 246+ 253 and 255, for systems using circuit-controllers.

This subclass is indented under subclass 126. Subject matter where the actuated devices are either crossing-gates, mine-doors, or curtains.

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111 125, 260, 293, and 473, and appropriate indented subclasses for signal structure.

This subclass is indented under subclass 125. Subject matter where the primary or controlling track-circuit is normally open.

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subclasses 58+ for systems of open-track-circuit control.
111 125, 260, 293, and 473, and appropriate indented subclasses, for signal structure.

This subclass is indented under subclass 128. Subject matter where an open circuit is closed by the car-wheels bridging two short parallel insulated sections of the traction-rails.

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89 for systems using short sectional rail-closures.
111 125, 260, 293, and 473, and appropriate indented subclasses, for signal structure.

This subclass is indented under subclass 125. Subject matter where the controlling track-circuit is normally closed.

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26 41, and appropriate indented subclasses, and 98, for normally closed track-circuits.
111 125, 260, 293, and 473, and appropriate indented subclasses, for signal structure.

This subclass is indented under the class definition. Subject matter having means for actuating switches, signals, locks, derails, and similar independently-movable units of this class in such manner as to insure predetermined sequences of operation so far as they may be needed to restrain the movement of all other devices which, if actuated, would give rise to a condition of danger.

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25 26 and 106, for locking in connection with block systems.
253 for switch or signal actuated controllers in which a plurality of circuits are closed or broken by the movement of the switch or signal and in which a predetermined sequence of operations is sometimes provided for.
401 for switch stands having rail lock and position indicating means.

This subclass is indented under subclass 131. Subject matter where electrical means are provided for actuating the movable units.

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22 28, 93, 96, 105, 114, 121, 125, 193, 202, 220, and 221, and appropriate indented subclasses, for the electric
actuation of signals.

This subclass is indented under subclass 132. Subject matter having electrical means provided for actuating the locks.

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15 19, 25, 26, 106, 130, and 146, and appropriate indented subclasses under subclass 131, for various types of interlocking.

This subclass is indented under subclass 133. Subject matter in which a definite route or itinerary is set up through a system of tracks by a smaller number of actuating levers or devices than would usually be required.
(1) Note. The term "program-locking" is sometimes applied to this system in foreign practice.

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155 156 and 157, for rod-saving devices.

This subclass is indented under subclass 133. Subject matter in which the actuating lever or device is prevented by electric locks from completing its movement, and from thereby releasing the other devices which it controls, until the actuated unit is in full normal or reversed position, whereupon a return-release-indication current is sent back, unlocking the actuating-lever and either effecting or permitting the completion of its movement.

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137 138, 141, and 142, for return-release-indication.
222 for return-indication-current generation.

This subclass is indented under subclass 132. Subject matter in which the locking is effected by mechanical connections between the actuating levers or devices.
(1) Note. This type of interlocking is known to the Railway Signal Association by the title "electromechanical interlocking".

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147 and appropriate indented subclasses for mechanical locking.

This subclass is indented under subclass 136. Subject matter in which the actuating lever or device is prevented by electric locks from completing its movement, and from thereby unlocking the other devices which it controls, until the actuated unit is in full normal or reverse position, whereupon a return-release-indication current is sent back, unlocking the actuating-lever and permitting or effecting the completion of its movement.

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135 138, 141, and 142, for return-release-indication.
222 for return-indication-current generation.

This subclass is indented under subclass 137. Subject matter in which the release-locking is applied to sliding members which actuate the circuit-closers.

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135 137, 141, and 142, for return-release indication.
222 for return-indication-current generation.

This subclass is indented under subclass 131. Subject matter in which fluid-pressure means are used for actuating the movable units.

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93 100, 101, 116, 257, 271, 272, and 361+, for systems using fluid-pressure.

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60, Power Plants, subclass 399 for a fluid- pressure actuator of general utility in which unsafeness, unreadiness or disarray prevents a manual change in the operative state of the system.
91, Motors: Expansible Chamber Type, appropriate subclasses, for the structure of the motor.
188, Brakes, subclass 153, for fluid-pressure-operated brakes applied to rail vehicles.
303, Fluid-Pressure and Analogous Brake System, appropriate subclasses, for systems for distributing fluid