Telephone signalling system having interruption preventive means

Details Telephone signalling system having interruption preventive means Telephone signalling system having interruption preventive means

1976-03-08

1977-08-09

Claffy, Kathleen H.

179 5P, H04M 1104

Patent

active

040412423

ABSTRACT:
A telephone signalling system having means for selectively disconnecting a telephone from a substation and connecting it to a message control unit including non-interrupt means responsive to current in the telephone wires when the telephone is in use for preventing disconnection of the telephone from the substation. Emergency override means are provided for disconnecting the telephone from the substation and connecting the telephone to the message control unit during an emergency irrespective of the telephone being in use.
The telephone signalling system in addition has means responsive to a test scanning signal to indicate proper connection of the telephone when it is connected to the message control unit.

REFERENCES:
patent: 3106611 (1963-10-01), Hilker
patent: 3304376 (1967-02-01), Truby
patent: 3484561 (1969-12-01), Matthews
patent: 3564148 (1971-02-01), Lee
patent: 3636280 (1972-01-01), Wetzel
patent: 3742141 (1973-06-01), Duncan
patent: 3777065 (1973-12-01), Galian
patent: 3865985 (1975-02-01), Stankus
patent: 3892922 (1975-07-01), Stankus

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