Digital telephone set having an emergency switching function and

Details Digital telephone set having an emergency switching function and Digital telephone set having an emergency switching function and

1991-05-21

1992-08-25

Dwyer, James L.

Telephonic communications

Centralized switching system

Switching controlled in response to called station...

379 2, 379 32, H04M 310

Patent

active

051425718

ABSTRACT:
A digital telephone set includes a digital telephone circuit and an emergency analog circuit. Normally, the digital telephone circuit is made active so that a handset provided in common therewith is connected to a digital transmission line. In an emergency, the emergency analog circuit is made active instead of the digital telephone circuit so that the handset is connected to an analog transmission line. A dial key pad unit and a speaker are provided in common with the digital telephone circuit and the emergency analog circuit.

REFERENCES:
patent: 4575584 (1986-03-01), Smith et al.
patent: 4853949 (1989-08-01), Schorr et al.
R. Sugioka et al., "Introduction of Digital PBX", Ohm corporation, Sep. 25, 1987, pp. 156-159.

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