Key telephone systems

Details Key telephone systems Key telephone systems

1976-08-05

1978-11-14

Cooper, William C.

179 18J, H04M 100

Patent

active

041257499

ABSTRACT:
The key button telephone system comprises a key service unit and a plurality of key telephone units. The key service unit and each key telephone unit are interconnected by a pair of cables, one of which is used as a talking circuit and the other is used to transmit and receive information signals and operating power. The key service unit comprises a line circuit for supervising the state of a line, a station unit for supervising the line circuit, and for supplying to the key telephone unit an information signal representing the state of the line and the operating power, a switching network controlled by the control output from the station unit for connecting the key telephone unit to the line, and a common control circuit for controlling the line circuit and the station unit. Each key telephone unit comprises a telephone circuit connected to the switching network, a telephone control circuit for supervising the state of the key telephone unit connected to the station unit, and a DC converter for converting a DC voltage supplied from the station unit into a predetermined DC voltage.

REFERENCES:
patent: 3244986 (1966-04-01), Rumble
patent: 3660611 (1972-05-01), Knollman et al.
patent: 3691310 (1972-09-01), Fenton
patent: 3843845 (1974-10-01), Ridley
patent: 3935396 (1976-01-01), Barsellotti et al.
patent: 3973085 (1976-08-01), Shiff
patent: 4010331 (1977-03-01), Taylor et al.
patent: 4027110 (1977-05-01), Takematsu et al.

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