Speakerphone device with auxiliary circuit for eliminating click

Details Speakerphone device with auxiliary circuit for eliminating click Speakerphone device with auxiliary circuit for eliminating click

1994-08-15

1996-05-07

Hofsass, Jeffery

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379395, 379421, H04M 102

Patent

active

055154310

ABSTRACT:
A speakerphone for a telephone circuit includes an output stage that comprises a loudspeaker amplifier coupled to a loudspeaker through a coupling capacitor. An auxiliary circuit includes a reference input element that provides first and second reference voltages which are used to charge the coupling capacitor to a given level prior to the input signal being coupled to the loudspeaker through the coupling capacitor to insure a click-free switch-on of the loudspeaker.

REFERENCES:
patent: 3706852 (1972-12-01), Angus
patent: 4025728 (1977-05-01), Jacobson
patent: 4304969 (1981-12-01), Walla
patent: 4371841 (1983-02-01), Eckert et al.
patent: 4400501 (1983-08-01), Jacobson
patent: 4640993 (1987-02-01), Whittaker
patent: 5070527 (1991-12-01), Lynn
patent: 5191606 (1993-03-01), Juang
patent: 5406636 (1995-04-01), Yamada et al.
patent: 5436588 (1995-07-01), Ghaffaripour
"An Integrated Telephone Speech Circuit Including a Line Fed Loudspeaker Amplifier", K. Eberhardt et al., ESSCI.2C '81, Sep. 1981, pp. 47-49.
WIRSUM, Siegfried: Verstarkerbau mit integrierten Schaltungen, RPB electronic-taschenbucher Nr. 331, Franzis-Verlag GmbH, Munchen, 5.Aufl., S.74-75.
Kramer; Moses: TN-Terminals im neuen Design. In: TN-Nachrichten, 1987, H.91, S.7-11.

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