Telephone interface circuit

Details Telephone interface circuit Telephone interface circuit

1989-11-15

1991-04-02

Ng, Jin F.

Telephonic communications

Supervisory or control line signaling

Signal reception at substation

379373, H04M 100

Patent

active

050051997

ABSTRACT:
A line powered telephone interface circuit answers an incoming call and, responsive to a command tone, routes the call to a selected terminal. If no command tone is received within a predetermined time period, low voltage audio signalling devices located near the conventional telephone sets are activated to alert the subscriber of an incoming call. The interface need not be connected to a separated supply source. The device is connected to a telephone line and to at least one plug connectable with a telephone set jack, the device being connected to various terminals. A detector detects the ring signal and a relay establishes connection with a telephone line as soon as the ring signal has been detected for a determined time duration. A combination timer/switcher circuit inhibits the ringing of the corresponding telephone set, and is associated with a sound transducer connected operable by a low voltage signal.

REFERENCES:
patent: 4266098 (1981-05-01), Novak
patent: 4409439 (1983-10-01), Gamble
patent: 4459435 (1984-07-01), Foldvary et al.
patent: 4639552 (1987-01-01), Hall

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