Click-free muting circuit for headset

Details Click-free muting circuit for headset Click-free muting circuit for headset

1999-10-15

2001-09-18

Chiang, Jack (Department: 2642)

Telephonic communications

Terminal

Having muting

Reexamination Certificate

active

06292560

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates in general to telephone headsets, and more particularly to a circuit for providing click-free muting of a telephone headset.
BACKGROUND OF THE INVENTION
Headsets are useful for hands free telephony in circumstances in which a person requires the use of his or her hands for operation of a computer, switchboard, etc. Headsets are usually connected to the handset port of a telephone set through an interface box. The interface box allows the user to select whether the headset or the handset is activated. Prior art interface boxes vary greatly in complexity, but most boxes include a headset volume control. Some such boxes are battery operated while others steal current from the microphone bias circuit.
One common problem associated with the use of telephone headsets is the generation of unpleasant clicking noises which occur when a mute button for the headset microphone is depressed or released. Another problem is insufficient “hard” muting.
According to one prior art approach, an AC coupled mute switch has been used to provide headset microphone muting. Unfortunately, this approach generally fails to sufficiently attenuate the microphone signal (i.e. no “hard” muting) and is not capable of performing headset switch detection which is a desirable feature of telephone headsets which can function also using a regular handset. DC coupled mute switches overcome the problem of headset switch detection but produce the aforenoted unpleasant click noise. Another approach involves the use of expensive battery powered microphone amplifier muting circuits. These circuits are normally implemented within cumbersome interface boxes attached to the telephone, and often do not provide a hard muting function.
SUMMARY OF THE INVENTION
According to the present invention, a circuit is provided which is capable of headset detection and microphone mute switch closure detection and which overcomes the above-discussed disadvantages of the prior art. The circuit provides click-free switching, 80 dB muting and is of inexpensive construction. No extra power supply is required, and the circuit is capable of providing headset detection.


REFERENCES:
patent: 4448074 (1984-05-01), Schmidt
patent: 4451706 (1984-05-01), Boeckmann
patent: 5353347 (1994-10-01), Irissou et al.
patent: 0202016 (1986-11-01), None
patent: 0592917 (1947-10-01), None
patent: 2317783 (1998-04-01), None

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