Abstract: A communications station for use in a distributed audio system having two Hall-effect integrated circuits mounted on a printed circuit hook switch board, the hook switch board mounted within a handset cradle of the communications station. The Hall-effect integrated circuits place the communications station on-hook or off-hook, depending on the amount of ambient magnetic flux. The ambient magnetic flux varies with the presence or absence of a handset in the cradle. Thus, if a handset containing a magnet is in the cradle, and the applied magnetic flux is greater than the predetermined flux necessary to affect the Hall-effect integrated circuit, the communications station will go on-hook. When the handset and the resultant flux is removed from the cradle, the Hall-effect integrated circuit will change state and the communications station will go off-hook.

Abstract: A field telephone system having a widely dispersed set of telephone lines including a page line pair and a party line pair, audio processing equipment including telephone handsets, handset amplifiers, receiver amplifiers and paging speaker amplifiers is designed to have improved voice transmission by provision of a narrow band FM carrier system. The FM carrier system includes a device for generating a carrier frequency signal, a modulator for modulating the carrier frequency with an audio signal derived from one of the handsets at a transmitting station and circuitry for transmitting the modulated signal over a line pair to a receiving station. The receiving station includes circuitry responsive to the transmitted signal and the carrier frequency signal for extracting the audio component of the transmitted signal and for processing the extracted audio signal and for providing the processed audio signal to a handset at the receiving station.

Abstract: A field telephone system having a widely dispersed set of telephone lines including a page line pair and a party line pair, audio processing equipment including telephone handsets, handset amplifiers, receiver amplifiers and paging speaker amplifiers is designed to have improved voice transmission by provision of a narrow band FM carrier system. The FM carrier system includes a device for generating a carrier frequency signal, a modulator for modulating the carrier frequency with an audio signal derived from one of the handsets at a transmitting station and circuitry for transmitting the modulated signal over a line pair to a receiving station. The receiving station includes circuitry responsive to the transmitted signal and the carrier frequency signal for extracting the audio component of the transmitted signal and for processing the extracted audio signal and for providing the processed audio signal to a handset at the receiving station.