Device for adding intercom functions to a phone system

Details Device for adding intercom functions to a phone system Device for adding intercom functions to a phone system

1987-05-04

1988-09-06

George, Keith E.

Telephonic communications

Substation or terminal circuitry

Hold circuit

379160, H04M 172

Patent

active

047698373

ABSTRACT:
A device for adding intercom functions to a residential or small business phone system uses existing telephone equipment and wiring. The device attaches to the incoming telephone line to switch telephone calls and generate user coded ringing signals. The invention allows the user to simultaneously use existing telephone equipment as an intercom system and for normal outside telephone use.

REFERENCES:
patent: 4088846 (1978-05-01), McEowen
patent: 4135063 (1979-01-01), Bosen
patent: 4158110 (1979-06-01), Ullakko et al.
patent: 4538031 (1985-08-01), Benning et al.
patent: 4572928 (1986-02-01), Nishimura et al.
patent: 4578540 (1986-03-01), Borg et al.
patent: 4588861 (1986-05-01), Teich
patent: 4674115 (1987-06-01), Kaleita et al.
Carter, "A Versatile New Intercom System", Bell Laboratories Record, Mar. 1958, pp. 81-85.

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