Key telephone system

Details Key telephone system Key telephone system

1974-12-03

1977-05-31

Claffy, Kathleen H.

H04M 172

Patent

active

040271102

ABSTRACT:
A telephone set scanning type key telephone system, in which a plurality of key telephone sets are connected in parallel, to a key service unit through control lines composed of a display information line, key information line, a terminal selecting line and a clock line. Each key telephone set comprises a display memory, a key memory, a terminal coincidence circuit and a gate. The terminal coincidence circuit collates a selecting code transmitted thereto from the key service unit through the terminal selecting line and applies clock pulses transmitted thereto from the key service unit through the clock line to the gate to drive the display memory and the key memory only when the selecting code is coincident with the terminal number. A driving signal transmitted in the serial configuration from the key service unit through the display information line is stored in the display memory to develope a display and, at the same time, the key information stored in the key memory is applied in the serial configuration to the key service unit through the key information line.

REFERENCES:
patent: 3549820 (1970-12-01), Knollman
patent: 3604857 (1971-09-01), Opferman
patent: 3701855 (1972-10-01), Reynolds
patent: 3787631 (1974-01-01), Lewis
patent: 3843845 (1974-10-01), Ridley

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