*****TBD*****

This subclass is indented under the class definition. Subject matter in which the frequency of the carrier is shifted among a plurality of discrete values in accordance with the modulating signal.

(1) Note. This subclass and its indents provide for a minimum shift keying (MSK) modulator which is a frequency shift keying modulator having phase continuity at the frequency transition points.

(2) Note. This subclass includes frequency shift keying modulators, per se. See the search class notes below for combinations with the subject matter of this subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

103+,

for a phase shift keying modulator.

SEE OR SEARCH CLASS:

375,	Pulse or Digital Communications, subclasses 272+ for a frequency shift keying system (i.e., transmitter and receiver), and subclasses 303+ for a frequency shift keying modulator combined with transmitting structure.

101	. Including logic element (e.g., logic gate or flip-flop):

This subclass is indented under subclass 100. Subject matter containing a component which performs a Boolean Algebraic operation.

(1) Note. Such components may be combinational or sequential (e.g., AND gates, OR gates or J-K flip-flops).

102	. Including discrete semiconductor device:

This subclass is indented under subclass 100. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

103	PHASE SHIFT KEYING MODULATOR OR QUADRATURE AMPLITUDE MODULATOR:

This subclass is indented under the class definition. Subject matter in which the phase of the carrier is shifted among a plurality of discrete angles in accordance with the modulating signal.

(1) Note. Also included here is the case where the phase and amplitude of the carrier are simultaneously shifted among a plurality of discrete angle/magnitude pairs (i.e., QAM).

(2) Note. This subclass includes phase shift keying modulators, or quadrature amplitude modulators, per se. See the search class notes below for combinations with the subject matter of this subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

100+,

for a frequency shift keying modulator.

SEE OR SEARCH CLASS:

375,	Pulse or Digital Communications, subclass 261 for a quadrature amplitude modulation system (i.e., transmitter and receiver), subclasses 279+ for a phase shift keying system, and subclass 308 for a phase shift keying modulator combined with transmitting structure.

104	. Including logic element (e.g., logic gate or flip-flop):

This subclass is indented under subclass 103. Subject matter containing a component which performs a Boolean Algebraic operation.

(1) Note. Such components may be combinational or sequential (e.g., AND gates, OR gates or J-K flip-flops).

105	. Including discrete semiconductor device:

This subclass is indented under subclass 103. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

106	PULSE OR INTERRUPTED CONTINUOUS WAVE MODULATOR:

This subclass is indented under the class definition. Subject matter producing a final output signal consisting of a repetitious pulse wave or a pulsed continuous wave having one or more of its characteristics varied in accordance with one or more modulating signals.

(1) Note. Examples of pulse waves are square waves, sawtooth waves, and trapezoidal waves.

(2) Note. If a system includes a pulse modulator, but the final output signal is a frequency, phase or an amplitude modulated wave, the modulator is classified in subclasses 117+, 144+ or 149+, respectively.

(3) Note. This subclass includes pulse modulators, per se. See the search class notes below for combinations with the subject matter of this subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

117+,	for a frequency modulator.
144+,	for a phase modulator.
149+,	for an amplitude modulator.

SEE OR SEARCH CLASS:

341,	Coded Data Generation or Conversion, subclasses 126 through 172or 143 for systems having a final output that is pulse code modulated (PCM) or delta modulated.
375,	Pulse or Digital Communications, appropriate subclasses for combinations of a pulse modulator with transmitting structure.

107	. Including stabilization or alternatively distortion, noise or other interference prevention, reduction, or compensation:

This subclass is indented under subclass 106. Subject matter including the neutralization of an undesirable characteristic of a pulse modulator or its signals.

(1) Note. Distortion may be introduced to the pulse modulating system in order to compensate for other inherent distortion.

(2) Note. The neutralized characteristic might be some form of system instability.

SEE OR SEARCH THIS CLASS, SUBCLASS:

123+,	for distortion or noise control in a frequency modulator.
159+,	for distortion or noise control in an amplitude modulator.

SEE OR SEARCH CLASS:

375,	Pulse or Digital Communications, subclasses 254 , 285 and 296 for noise or distortion control in a system or transmitter.

108	. Plural modulation:

This subclass is indented under subclass 106. Subject matter having a plurality of modulators, modulating signals, or diverse output modulation types simultaneously present or individually selectable.

(1) Note. At least one final output signal must be a pulse modulated signal for classification herein.

(2) Note. Multiplex pulse modulators, per se, are classified here.

SEE OR SEARCH THIS CLASS, SUBCLASS:

119+,	for plural modulation in a frequency modulator.
145,	for plural modulation in a phase modulator.
151+,	for plural modulation in an amplitude modulator.

SEE OR SEARCH CLASS:

370,	Multiplex Communications, appropriate subclasses and particularly subclass 205 for combined pulse width and pulse position modulation, subclass 212 for a multiplex transmitter using pulse width modulation and subclass 213 for multiplex transmitter using pulse position modulation.

109	. Pulse width modulator:

This subclass is indented under subclass 106. Subject matter producing a pulse wave output signal in which the pulse width (duration) is varied by the modulating signal.

SEE OR SEARCH CLASS:

375,	Pulse or Digital Communications, subclass 238 for a combination of pulse width modulator with transmitting structure.

110	.. Including discrete semiconductor device having three or more electrodes:

This subclass is indented under subclass 109. Subject matter utilizing a device with three external connection points where the constituent portions of the device are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

111	.. Including electron discharge device:

This subclass is indented under subclass 109. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

112	. Pulse position, frequency, phase, or spacing modulator:

This subclass is indented under subclass 106. Subject matter producing a pulse wave output signal in which the relative positions of the pulses, the frequency (repetition rate) of the pulses, the phase of the pulses, or the spacing (time) between the pulses is varied by the modulating signal.

SEE OR SEARCH CLASS:

375,	Pulse or Digital Communications, subclass 239 for a combination of pulse position, frequency or spacing modulator with transmitting structure.

113	.. Including discrete semiconductor device having three or more electrodes:

This subclass is indented under subclass 112. Subject matter utilizing a device with three external connection points where the constituent portions of the device are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

114	.. Including electron discharge device:

This subclass is indented under subclass 112. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

115	. Pulse amplitude modulator:

This subclass is indented under subclass 106. Subject matter producing a pulse wave output signal in which the amplitude of the pulses is controlled by the modulating signal.

SEE OR SEARCH CLASS:

375,	Pulse or Digital Communications, subclasses 300+ for a combination of pulse amplitude modulator with transmitting structure, and subclasses 268+ for a pulse amplitude modulation system (i.e., transmitter and receiver).

116	.. Including discrete semiconductor device having three or more electrodes:

This subclass is indented under subclass 115. Subject matter utilizing a device with three external connection points where the constituent portions of the device are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

117	FREQUENCY MODULATOR:

This subclass is indented under the class definition. Subject matter in which the frequency of the carrier is varied over a continuum of values in accordance with the modulating signal.

(1) Note. This subclass includes frequency modulators, per se. See the search class notes below for combinations with the subject matter of this subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

106+,	for a pulse modulator.
144+,	for a phase modulator.
149+,	for an amplitude modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclasses 42+ for frequency modulation in a system with separated transmitter and receiver, and subclasses 110+ for a combination of frequency modulator with transmitting structure.

118	. Including measuring or indicating:

This subclass is indented under subclass 117. Subject matter combined with apparatus producing a qualitative or quantitative output representative of a characteristic of the modulator or its signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:

150,	for measuring in an amplitude modulator.

SEE OR SEARCH CLASS:

331,	Oscillators, subclass 64 for an oscillator with indicator.
455,	Telecommunications, subclasses 67.11 through 67.7for measuring or testing in a system with separated transmitter and receiver and subclasses 115.1-115.4 for measuring or testing of a telecommunications transmitter.

119	. Plural modulation:

This subclass is indented under subclass 117. Subject matter having a plurality of modulators, modulating signals, or diverse output modulation types simultaneously present or individually selectable.

(1) Note. At least one final output signal must be a frequency modulated signal.

(2) Note. Multiplex frequency modulators, per se, are classified here.

SEE OR SEARCH THIS CLASS, SUBCLASS:

108,	for plural modulation in a pulse modulator.
145,	for plural modulation in a phase modulator.
151+,	for plural modulation in an amplitude modulator.

SEE OR SEARCH CLASS:

370,	Multiplex Communications, appropriate subclasses and particularly subclasses 204+ for plural diverse modulation techniques, subclass 215 for multiplex transmitter using phase modulation and subclass 483 for a multiplex transmitter using frequency modulation.
455,	Telecommunications, subclass 61 for plural modulation where a single message is conveyed between a separated transmitter and receiver and subclass 102 for plural modulation in a telecommunications transmitter.

120	.. Including amplitude modulation:

This subclass is indented under subclass 119. Subject matter in which at least one modulator is an amplitude modulator or in which amplitude modulation is produced in addition to the frequency modulation.

SEE OR SEARCH THIS CLASS, SUBCLASS:

145,	for a phase modulator which includes an amplitude modulator.

121	... Including electron discharge device:

This subclass is indented under subclass 120. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

122	.. Including electron discharge device:

This subclass is indented under subclass 119. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

123	. Including stabilization or alternatively distortion, noise or other interference prevention, reduction, or compensation:

This subclass is indented under subclass 117. Subject matter including the neutralization of an undesirable characteristic of a frequency modulator or its signals.

(1) Note. In some instances, distortion may be introduced to the FM system in order to compensate for other inherent distortion.

(2) Note. The neutralized characteristic might be some form of system instability.

SEE OR SEARCH THIS CLASS, SUBCLASS:

107,	for distortion or noise control in a pulse modulator.
159+,	for distortion or noise control in an amplitude modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclasses 63.1 through 65and 501-506 for noise control in a telecommunication system with separated transmitter and receiver, and subclasses 114.1-114.3 for harmonic radiation control in a transmitter.

124	.. Nonlinearity reduction or compensation:

	This subclass is indented under subclass 123. Subject matter which diminishes the undesired effects of a modulator element or circuit whose output is not directly proportional to its input.

125	.. Automatic amplitude stabilization or control:

This subclass is indented under subclass 123. Subject matter where undesired signal amplitude variations are controlled without human intervention.

(1) Note. This might include, for example, suppression of undesired amplitude modulation.

SEE OR SEARCH THIS CLASS, SUBCLASS:

155+,

for amplitude control in an amplitude modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclass 116 for control of carrier amplitude in a transmitter.

126	.. Automatic frequency stabilization or control:

This subclass is indented under subclass 123. Subject matter in which undesired signal frequency variations are controlled without human intervention.

(1) Note. Often the frequency being controlled is that of the unmodulated carrier.

SEE OR SEARCH THIS CLASS, SUBCLASS:

161,	for frequency control in an amplitude modulator.

SEE OR SEARCH CLASS:

331,	Oscillators, subclasses 1+ for automatic frequency control of an oscillator.
455,	Telecommunications, subclasses 75+ for frequency stabilization in a transceiver, subclass 113 for frequency control of a frequency modulated transmitter, and subclass 119 for stabilizing the carrier frequency in a telecommunications transmitter.

127	... Phase or frequency locked loop:

	This subclass is indented under subclass 126. Subject matter in which a stable frequency is attained by utilizing a phase or frequency locked loop.

128	.... Modulating signal applied to plural elements of the loop:

	This subclass is indented under subclass 127. Subject matter in which the modulating signal is injected into a plurality of points within the locked loop.

129	. Including microwave or distributed parameter structure:

This subclass is indented under subclass 117. Subject matter utilizing a structure or device which is peculiar to microwave frequencies or which has resistance, inductance or capacitance not concentrated in lumped circuit elements.

SEE OR SEARCH THIS CLASS, SUBCLASS:

163+,

for similar structure in an amplitude modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclass 111 for distributed parameter structure in a frequency modulated transmitter.

130	.. With discrete semiconductor device:

This subclass is indented under subclass 129. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

131	.. With electron discharge device:

This subclass is indented under subclass 129. Subject matter combined with a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

132	... Magnetron type:

This subclass is indented under subclass 131. Subject matter in which an electron beam within the discharge device is subject to a magnetic field.

SEE OR SEARCH CLASS:

315,	Electric Lamp and Discharge Devices: Systems, subclasses 5.13 and 39.51+ for a magnetron combined with diverse circuit element.
331,	Oscillators, subclass 5 for automatic frequency control of a magnetron oscillator and subclasses 86+ for a magnetron oscillator, per se.

133	... Klystron type:

This subclass is indented under subclass 131. Subject matter where the discharge device includes structure to vary the relative velocity of different longitudinal portions of the electron beam resulting in electron bunching.

SEE OR SEARCH CLASS:

315,	Electric Lamp and Discharge Devices: Systems, subclasses 5+ for a cathode- ray tube circuit where the ray traverses a hollow distributed parameter device and particularly indented thereunder subclasses 5.21+, 5.46+ and 5.53+ for tuning thereof.
331,	Oscillators, subclasses 6+ for automatic frequency control in a klystron oscillator and subclass 83 for a klystron oscillator, per se.

134	... Travelling wave type:

This subclass is indented under subclass 131. Subject matter wherein the discharge device has structure to slow a travelling electromagnetic wave to more closely match the velocity of an electron beam with which it is interacting.

SEE OR SEARCH CLASS:

315,	Electric Lamp and Discharge Devices: Systems, subclasses 3.5+ for travelling wave tube combined with a delay transmission line.
331,	Oscillators, subclass 82 for a travelling wave-tube type oscillator.

135	. Including discrete semiconductor device:

This subclass is indented under subclass 117. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

136	.. With varactor:

This subclass is indented under subclass 135. Subject matter in combination with a variable capacitance diode.

SEE OR SEARCH CLASS:

257,	Active Solid-State Devices (e.g., Transistors, Solid-State Diodes), subclasses 312 , 480, and 595-602 for voltage variable capacitive type active semiconductor devices.

137	. Including electron discharge device:

This subclass is indented under subclass 117. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

138	.. Particular oscillator circuit:

This subclass is indented under subclass 137. Subject matter including details of an associated frequency source.

(1) Note. Mere mention of an oscillator exclusive of detail is insufficient for classification herein.

SEE OR SEARCH CLASS:

331,	Oscillators, appropriate subclasses for an oscillator, per se.

139	... Crystal oscillator type:

This subclass is indented under subclass 138. Subject matter in which frequency generation is controlled by a crystal resonator such as a piezoelectric crystal.

SEE OR SEARCH CLASS:

331,	Oscillators, subclasses 73 , 116, 139, and 154+ for piezoelectric-type oscillators.

140	.... With separate modulator tube (e.g., reactance tube):

	This subclass is indented under subclass 139. Subject matter where an electron discharge device distinct from the crystal oscillator performs the actual modulation.

141	... L-C oscillator type:

	This subclass is indented under subclass 138. Subject matter in which frequency generation is accomplished by an inductive-capacitive network.

142	.... With separate modulator tube (e.g., reactance tube):

	This subclass is indented under subclass 141. Subject matter where an electron discharge device distinct from the L-C oscillator performs the actual modulation.

143	..... Plural modulator tubes:

	This subclass is indented under subclass 142. Subject matter having a plurality of such distinct modulator tubes.

144	PHASE MODULATOR:

This subclass is indented under the class definition. Subject matter in which the phase of the carrier is varied over a continuum of values in accordance with the modulating signal.

(1) Note. This subclass includes phase modulators, per se. See search class notes below for combinations with the subject matter of this subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

106+,	for a pulse modulator.
117+,	for a frequency modulator.
149+,	for an amplitude modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclasses 42+ for phase modulation in a system with separated transmitter and receiver, and subclasses 110+ for a combination of a phase modulator with transmitting structure.

145	. Including amplitude modulator:

This subclass is indented under subclass 144. Subject matter in which at least one modulator is an amplitude modulator or in which amplitude modulation is produced in addition to phase modulation.

SEE OR SEARCH THIS CLASS, SUBCLASS:

108,	for plural modulation in a pulse modulator.
119+,	for plural modulation in a frequency modulator.
151+,	for plural modulation in an amplitude modulator.

SEE OR SEARCH CLASS:

370,	Multiplex Communications, appropriate subclasses and particularly subclasses 204+ for plural diverse modulation techniques, subclass 215 for a multiplexer using phase modulation, subclass 483 for a multiplexer using frequency modulation, and subclass 533 for a multiplexer using pulse amplitude modulation.
455,	Telecommunications, subclass 61 for plural modulation where a single message is conveyed between a separated transmitter and receiver and subclass 102 for plural modulation in a telecommunications transmitter.

146	. Including discrete semiconductor device:

This subclass is indented under subclass 144. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

147	. Including electron discharge device:

This subclass is indented under subclass 144. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

148	.. Push-pull circuit:

	This subclass is indented under subclass 147. Subject matter wherein there are two electrical paths with common output each of which contains an electron discharge device and in which the respective voltages are 180o out of phase with respect to the other.

149	AMPLITUDE MODULATOR:

This subclass is indented under the class definition. Subject matter in which the amplitude of the carrier is varied over a continuum of values in accordance with the modulating signal.

(1) Note. If a system includes an amplitude modulator, but the final output signal is a pulse modulated, frequency modulated or phase modulated wave, the modulator is classified in subclasses 106+, 117+ or 144+, respectively.

(2) Note. This subclass includes amplitude modulators, per se. See the search class notes below for combinations with the subject matter of this subclass.

SEE OR SEARCH THIS CLASS, SUBCLASS:

106+,	for a pulse modulator.
117+,	for a frequency modulator.
144+,	for a phase modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclasses 108+ for amplitude modulation in a telecommunications transmitter.

150	. Including measuring or indicating:

This subclass is indented under subclass 149. Subject matter combined with apparatus producing a qualitative or quantitative output representative of a characteristic of the modulator or its signals.

SEE OR SEARCH THIS CLASS, SUBCLASS:

118,	for measuring in a frequency modulator.

SEE OR SEARCH CLASS:

331,	Oscillators, subclass 64 for an oscillator with indicator.
455,	Telecommunications, subclasses 67.11 through 67.7for measuring or testing in a system with separated transmitter and receiver and subclasses 115.1-115.4 for measuring or testing of a telecommunications transmitter.

151	. Plural modulation:

This subclass is indented under subclass 149. Subject matter having a plurality of modulators, modulating signals, or diverse output modulation types simultaneously present or individually selectable.

(1) Note. At least one final output signal must be an amplitude modulated carrier wave.

(2) Note. Multiplex amplitude modulators, per se, are classified here.

SEE OR SEARCH THIS CLASS, SUBCLASS:

108,	for plural modulation in a pulse modulator.
119+,	for plural modulation in a frequency modulator.
145,	for plural modulation in a phase modulator.

SEE OR SEARCH CLASS:

370,	Multiplex Communications, appropriate subclasses and particularly subclasses 204+ for plural diverse modulation techniques, and subclass 533 for a multiplexer using pulse amplitude modulation.
455,	Telecommunications, subclass 61 for plural modulation where a single message is conveyed between a separated transmitter and receiver and subclass 102 for plural modulation in a telecommunications transmitter.

152	.. Including discrete semiconductor device:

This subclass is indented under subclass 151. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

153	.. Including electron discharge device:

This subclass is indented under subclass 151. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

154	... Push-pull circuit:

	This subclass is indented under subclass 153. Subject matter wherein there are two electrical paths with common output each of which contains an electron discharge device and in which the respective voltages are 180 degrees out of phase with respect to the other.

155	. Percent modulation control or automatic amplitude control of carrier or modulating signal:

This subclass is indented under subclass 149. Subject matter in which amplitude control is exerted on the carrier, the modulating signal, or the ratio therebetween without human intervention.

SEE OR SEARCH THIS CLASS, SUBCLASS:

125,	for amplitude control in a frequency modulator.

SEE OR SEARCH CLASS:

331,	Oscillators, subclasses 109 and 182+ for an oscillator with amplitude control.
455,	Telecommunications, subclass 116 for control of carrier amplitude in a transmitter.

156	.. Overmodulation prevention:

	This subclass is indented under subclass 155. Subject matter in which the automatic amplitude control maintains the ratio of the modulating signal amplitude to the carrier signal amplitude at a value of one or less.

157	.. Average carrier amplitude controlled by modulating signal:

	This subclass is indented under subclass 155. Subject matter in which the average unmodulated carrier amplitude is adjusted to reflect the average modulating signal amplitude.

158	.. Carrier output suppressed during absence of modulating signal:

This subclass is indented under subclass 155. Subject matter in which the automatic control eliminates the carrier in response to a lack of modulating signal.

SEE OR SEARCH THIS CLASS, SUBCLASS:

167+,

for a suppressed carrier, double sideband amplitude modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclass 116 for carrier amplitude control in a telecommunications transmitter.

159	. Including stabilization or alternatively distortion, noise or other interference prevention, reduction or compensation:

This subclass is indented under subclass 149. Subject matter including the neutralization of an undesirable characteristic of an amplitude modulator or its signals.

(1) Note. In some instances, distortion may be introduced to the AM system in order to compensate for other inherent distortion.

(2) Note. The neutralized characteristic might be some form of system instability.

SEE OR SEARCH THIS CLASS, SUBCLASS:

107,	for distortion or noise control in a pulse modulator.
123+,	for distortion or noise control in a frequency modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclasses 63.1 through 65and 501-506 for noise control in a telecommunication system with separated transmitter and receiver, and subclasses 114.1-114.3 for harmonic radiation control in a transmitter.

160	.. Reduction or compensation of nonlinearity in modulation characteristic:

	This subclass is indented under subclass 159. Subject matter which diminishes the undesired effects of a modulator element or circuit whose output is not directly proportional to its input.

161	.. Reduction of carrier phase or frequency variations or modulation:

This subclass is indented under subclass 159. Subject matter in which undesired fluctuations of either the phase or frequency of the carrier are reduced.

SEE OR SEARCH THIS CLASS, SUBCLASS:

126+,

for frequency control in a frequency modulator.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclasses 75+ for frequency stabilization in a transceiver, subclass 113 for frequency control of a frequency modulated transmitter, and subclass 119 for stabilizing the carrier frequency in a telecommunications transmitter.

162	.. Using feedback to reduce distortion, noise or other interference:

	This subclass is indented under subclass 159. Subject matter in which a feedback signal is used to remove or control distortion.

163	. Including microwave or distributed parameter structure:

This subclass is indented under subclass 149. Subject matter utilizing a structure or device which is peculiar to microwave frequencies or which has resistance, inductance or capacitance not concentrated in lumped circuit elements.

SEE OR SEARCH THIS CLASS, SUBCLASS:

129+,

for similar structure in a frequency modulator.

164	.. With discrete semiconductor device:

This subclass is indented under subclass 163. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

165	.. With electron discharge device:

This subclass is indented under subclass 163. Subject matter combined with a device which has electrical current flow between two spaced electrodes in a gas, vapor, or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

166	... Magnetron type:

This subclass is indented under subclass 165. Subject matter in which an electron beam within the discharge device is subject to a magnetic field.

SEE OR SEARCH CLASS:

315,	Electric Lamp and Discharge Devices: Systems, subclasses 5.13 and 39.51+ for a magnetron combined with diverse circuit element.
331,	Oscillators, subclass 5 for automatic frequency control in a magnetron oscillator and subclasses 86+ for a magnetron oscillator, per se.

167	. Suppressed carrier double sideband type:

This subclass is indented under subclass 149. Subject matter in which the carrier is suppressed continuously or intermittently and both sidebands are intact.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclass 46 for a suppressed carrier system having separated transmitter and receiver and subclass 109 for a suppressed carrier amplitude modulated transmitter.

168	.. Including discrete semiconductor device:

This subclass is indented under subclass 167. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

169	.. Including electron discharge device:

This subclass is indented under subclass 167. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

170	. Single or vestigial sideband type:

This subclass is indented under subclass 149. Subject matter in which the final output contains less than two complete sidebands with or without the carrier.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclass 47 for a single or vestigial sideband system with separated transmitter and receiver and subclass 109 for a single or vestigial sideband amplitude modulated transmitter.

171	.. Including electron discharge device:

This subclass is indented under subclass 170. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

172	. Modulating signal applied to a bridge circuit:

	This subclass is indented under subclass 149. Subject matter in which the carrier is applied to an impedance bridge in which the impedance of at least one branch is varied in accordance with the modulating signal.

173	. Magnetic field varied by modulating signal:

This subclass is indented under subclass 149. Subject matter in which the amplitude of the carrier is varied by varying a magnetic field in accordance with the modulating signal.

(1) Note. Devices which may be used to vary a magnetic field include saturable reactors and transformers.

174	. Resistive or dissipative device controlled by modulating signal (e.g., loss modulator):

This subclass is indented under subclass 149. Subject matter in which the energy of the carrier is variably absorbed, diverted or scattered in accordance with the modulating signal.

SEE OR SEARCH CLASS:

455,	Telecommunications, subclass 106 for a transmitter utilizing absorption modulation.

175	. Variable reactance controlled by modulating signal:

This subclass is indented under subclass 149. Subject matter in which the amplitude of the carrier is varied by varying a reactance in accordance with the modulating signal.

(1) Note. The variable reactance might be part of a tuning circuit, variation of which may be used to vary the gain of a circuit and thereby the amplitude of the carrier.

176	. Nonlinear device controlled by modulating signal:

This subclass is indented under subclass 149. Subject matter which includes a circuit element having an impedance which is not directly proportional to the current passing through it or the voltage applied to it and which controls the amplitude of the carrier in accordance with the modulating signal.

(1) Note. Examples of nonlinear devices could be diodes, nonlinear crystals, thyrite resistors, or electronic tubes.

177	.. Nonlinear discrete semiconductor device:

	This subclass is indented under subclass 176. Subject matter in which the controlled circuit element is an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

178	. Including discrete semiconductor device:

This subclass is indented under subclass 149. Subject matter containing an electrical device whose constituent portions are constructed from solid material having room temperature conductivity between that of a conductor and an insulator and which conductivity is typically modified through the addition of small amounts of dopant.

(1) Note. This might include, for example, semiconductor diodes or transistors of diverse type.

179	. Including electron discharge device:

This subclass is indented under subclass 149. Subject matter utilizing a device which has electrical current flow between two spaced electrodes in a gas, vapor or vacuum.

(1) Note. This might include, for example, vacuum or gas tubes such as diodes, triodes or pentodes.

(2) Note. Additional control electrodes may be present.

180	.. Push-pull circuit:

	This subclass is indented under subclass 179. Subject matter wherein there are two electrical paths with common output each of which contains an electron discharge device and in which the respective voltages are 180 degrees out of phase with respect to the other.

181	.. Plate circuit modulation:

This subclass is indented under subclass 179. Subject matter including an electronic tube which generates or amplifies the carrier, and in which the modulating signal is applied to the anode circuit of the tube or controls a circuit element in the anode circuit.

(1) Note. This subclass includes circuits in which a variable voltage under control of the modulating signal is added to the anode supply voltage.

182	.. Grid circuit modulation:

	This subclass is indented under subclass 179. Subject matter including an electronic tube which generates or amplifies the carrier, and in which the modulating signal is applied to the grid circuit of the tube or controls a circuit element in the grid circuit.

183	MODULATION CONVERTER HAVING PRE-MODULATED INPUT (E.G., FM TO AM):

This subclass is indented under the class definition. Subject matter in which the input to a system is a repetitious electrical wave which has had a characteristic varied in accordance with a modulating signal, and in which the output of the system is a repetitious electrical wave having a different characteristic varied.

(1) Note. The combination of subject matter of this subclass with a subsequent demodulator is classified in Class 329.

SEE OR SEARCH THIS CLASS, SUBCLASS:

108,

119-122, 145, and 151-154, for systems having a plurality of diverse-type modulators wherein the input of a first modulator is an intelligence and the output of this modulator forms the input of a second modulator whose output is a different form of modulation from its input; and the final output of these systems is pulse, frequency, phase, or amplitude modulated, respectively.

SEE OR SEARCH CLASS:

341,	Coded Data Generation or Coversion, subclasses 126 through 172and 143 for systems having outputs that are pulse code modulated (PCM) or delta modulated.
455,	Telecommunications, appropriate subclasses for diverse-type conversion in a telecommunication transmitter or receiver.