US PATENT SUBCLASS 455 / 227
.~ Responsive to an input signal of particular predetermined frequency

Current as of: June, 1999
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455 /   HD   TELECOMMUNICATIONS

130  DF  RECEIVER OR ANALOG MODULATED SIGNAL FREQUENCY CONVERTER {24}
227.~ Responsive to an input signal of particular predetermined frequency {2}
228  DF  .~.~> Responsive to specified modulation (e.g., call alarm, Conelrad)
229  DF  .~.~> Responsive to carrier absence or presence

DEFINITION

Classification: 455/227

Responsive to an input signal of particular predetermined frequency:

(under subclass 130) Subject matter wherein the receiver is permanently adjusted in such a manner as to have a response to signals having a carrier wave of a predetermined frequency or a carrier signal having a predetermined identifying modulation frequency superimposed thereon.

(1) Note. The subject matter found in this subclass is restricted to receivers responsive to a particular preselected input activating signal of a predetermined frequency or other preselected characteristic only.

SEE OR SEARCH THIS CLASS, SUBCLASS:

26+, for unauthorized use prevention systems whereby only a particular receiver means is enabled to receive a message transmitted from the transmitter.

31.1+, for systems with receiver selection.

140, for a plurality of receivers selectively activated.

229, for receivers with alarm or alerting means.

352+, for remotely controlled receivers. SEE OR SEARCH CLASS

307, Electrical Transmission or Interconnection Systems,

129, for frequency responsive switching systems.

327, Miscellaneous Active Electrical Nonlinear Devices, Circuits, and Systems,

1+, for miscellaneous discriminating circuits and particularly subclasses 39+ for frequency discriminating.

333, Wave Transmission Lines and Networks,

165, 212 for wave filters, per se, comprised of passive elements.

340, Communications: Electrical,

171, for frequency responsive remote control signal devices; and subclass 539 for automatic alarm systems operated via radio link.

343, Communications: Radio Wave Antennas,

5+, for object detection systems responsive to returned signals; and subclasses 113+ for direction finding receiver systems responsive to a particular input signal. 346, Recorders,

37, for recording systems with control means of the radio receiver type.

361, Electricity: Electrical Systems and Devices,

182+, for electric control circuits for relays which are frequency responsive.

375, Pulse or Digital Communications,

316+, for pulse receivers which may be selectively responsive.

380, Cryptography, appropriate subclasses for cryptos:graphic prevention of signal unauthorized use.