Internal telephone intercom system

Details Internal telephone intercom system Internal telephone intercom system

1991-06-28

1992-06-23

Dwyer, James L.

Telephonic communications

Private or single line system

Doorbell system

379 64, 379 66, 379171, 379387, H04M 160, H04M 900, H04M 100

Patent

active

051250268

ABSTRACT:
An internal telephone intercom system including means for connecting to a dedicated telephone communication line, a plurality of telephone sets connected to the line and adapted for telephone communications with locations external to said dedicated line, an audio receiving means at each telephone set for receiving audio signals from a microphone within said telephone set, a radio frequency generator means for generating a carrier frequency and amplitude modulated responsive to said audio signals with said modulated signal being multiplexed on said dedicated line, an audio expander for receiving a modulated signal from the radio frequency generator means and producing an audio signal responsive to audio sounds at a speaker.

REFERENCES:
patent: 2323033 (1943-06-01), Hagen
patent: 3743791 (1973-07-01), Duff et al.
patent: 4380687 (1983-04-01), Stewart
patent: 4408102 (1983-10-01), Lumpkin
patent: 4523307 (1985-06-01), Brown et al.
patent: 4730306 (1988-03-01), Uchida
patent: 4734932 (1988-03-01), Lott
patent: 4891605 (1990-01-01), Tirkel
patent: 4908855 (1990-03-01), Ohga et al.

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