Key telephone communication path interface

Details Key telephone communication path interface Key telephone communication path interface

1976-07-28

1977-08-02

Claffy, Kathleen H.

H04M 172

Patent

active

040397637

ABSTRACT:
There is disclosed an electronic key telephone line circuit having a communication path interface capable of being connected across the communication pair during both the busy and idle conditions of the line circuit. The circuit is arranged such that both the pre-ring test and the impedance test from the central switching machine are satisfied while at the same time presenting a linear impedance for communication signals. Opto isolators are used and coupled with lightning surge protection and a capacitance and resistance bridge to allow permanent connection across the communication pairs. The circuit includes a hold bridge impedance, separate from the signal detection circuitry, switchable across the communication path.

REFERENCES:
patent: 3816670 (1974-06-01), Marshall
patent: 3856994 (1974-12-01), Ozechoski
patent: 3895192 (1975-07-01), Angner et al.
patent: 3925625 (1975-12-01), Angner et al.
patent: 3946146 (1976-03-01), Brown et al.

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