Key telephone system

Details Key telephone system Key telephone system

1977-01-03

1978-05-30

Claffy, Kathleen H.

H04M 172

Patent

active

040925013

ABSTRACT:
A key telephone system, in which at least one CO line, at least one intercomm. line and control lines are arranged between a key service unit and a plurality of key telephone sets. The key service unit is provided with a scanning circuit for generating multiplexed code units indicating the connection state of each channel of said CO line and said intercomm. line in a time-division manner to scan the key telephone sets. The key service unit further includes means for transmitting the code unit to each key telephone set through said control lines. Each of the key telephone sets includes a decoder for decoding the code units thus transmitted to obtain individual indication signals indicating the states of each channel.

REFERENCES:
patent: 3244815 (1966-04-01), Anderson et al.
patent: 3385935 (1968-05-01), Anderson et al.
patent: 3519757 (1970-07-01), Anderson et al.
patent: 3549820 (1970-12-01), Knollman
patent: 3843845 (1974-10-01), Ridley
patent: 3973085 (1976-08-01), Shiff

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