Hands free telephone with switchable gain in the two speech sign

Details Hands free telephone with switchable gain in the two speech sign Hands free telephone with switchable gain in the two speech sign

1982-05-10

1984-06-12

Pellinen, A. D.

Electrical audio signal processing systems and devices

Hearing aids, electrical

Specified casing or housing

381 93, 330151, H04M 908, H04R 302

Patent

active

044543840

ABSTRACT:
"Hands free" telephone sets in which there is connected in parallel with the terminals (A) and (B) of a first path (C.sub.1) comprising the coupling circuit of the telephone set in series with a controllable amplifier (11) of the receiving path (6), a second path (C.sub.2) comprising a controllable amplifier (12) which is controlled by a linear regulator (13) which keeps its output signal constant. The gains of the two amplifiers (11) and (12) respond to each other. A device is provided so as to ensure that the gain in the second path remains higher than the gain in the first path. A third controllable amplifier (5) is provided between the microphone (4) and the input terminal (A) which is used in common by the first and second paths; the said means (14) are adjusted in such a way that the electro-acoustic loop which is closed by the second path (C.sub.2) is permanently the source of non-annoying oscillations. By inducing a gain variation of the second amplifier (6) a gain variation in the opposite sense is produced in the receiving path, it being possible for these two variations to have accurately the same amplitudes.

REFERENCES:
patent: 3825843 (1974-07-01), Felsberg
patent: 4064462 (1977-12-01), Goghler et al.
patent: 4081620 (1978-03-01), Goodman et al.
patent: 4081622 (1978-03-01), Clark et al.
patent: 4382398 (1983-05-01), O'Neill

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