05125026 is referenced by 14 patents and cites 9 patents.

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.

Title
Internal telephone intercom system
Application Number
455602
Publication Number
5125026
Application Date
June 28, 1991
Publication Date
June 23, 1992
Inventor
Wayne T Holcombe
Palo Alto
CA, US
Agent
Thomas E Schatzel
Assignee
H & K Devices
CA, US
IPC
H04M 1/00
H04M 9/00
H04M 1/60
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