Muting circuit for telephone answering machine

Details Muting circuit for telephone answering machine Muting circuit for telephone answering machine

1988-01-04

1990-07-10

Dwyer, James L.

Telephonic communications

Audio message storage, retrieval, or synthesis

379 79, 379161, 379184, H04M 165

Patent

active

049411667

ABSTRACT:
A voltage breakdown circuit is connected in series between telephone answering machine circuitry and a telephone line. The voltage breakdown device becomes conductive only when the voltage across its terminals exceeds a predetermined level. If a telephone connected to the same telephone line as the answering machine circuitry is placed in the off hook condition, the voltage across the voltage breakdown device falls below the threshold level and the answering machine circuitry is effectively cut off from the telephone line. The voltage breakdown circuit is also useful in defeating automatic recording equipment placed in parallel with a telephone. Such automatic recording equipment is automatically disabled whenever the voltage across the tip in ring terminals of a telephone line is above a predetermined level. By placing the voltage breakdown circuit in series with a telephone which is to be protected from such taping, an automatic recording device connected in parallel with the telephone will automatically be disabled when the telephone is placed in the off hook condition.

REFERENCES:
patent: 3514544 (1970-05-01), Chambers, Jr.
patent: 3716673 (1973-02-01), Meri
patent: 4000375 (1976-12-01), Kawamura
patent: 4074081 (1978-02-01), Humm
patent: 4726048 (1988-02-01), Waldman et al.
patent: 4747128 (1988-05-01), Chan et al.

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