Telephone handset interface for device having audio input

Details Telephone handset interface for device having audio input Telephone handset interface for device having audio input

1994-11-28

1995-10-03

Hofsass, Jeffery A.

Telephonic communications

Terminal accessory or auxiliary equipment

With circuit connection to terminal

379 93, 379394, H04M 900

Patent

active

054558590

ABSTRACT:
An interface between a telephone handset and an external device having both data and audio inputs and outputs, such as a voice-over-data modem, allows a user to speak and listen through the handset of the telephone instrument. The interface also allows a voice-over-data modem to be connected to a PBX-type telephone system. The interface includes a filter circuit that allows the audio-frequency signal generated by the handset microphone to pass through to the external device while blocking DC along that path. The circuit also allows the DC bias voltage provided by the telephone base to pass through to the handset microphone while blocking audio-frequency signals on that path. The interface may also include a switching circuit that forms direct electrical connections between the telephone handset and the telephone base when the external device is not in a mode in which it can communicate data, e.g., when a voice-over-data modem is in an on-hook state.

REFERENCES:
patent: 4825465 (1989-04-01), Ryan
patent: 4864567 (1989-09-01), Giorgio
patent: 4907267 (1990-03-01), Gutzmer
patent: 4951312 (1990-08-01), Tanikawa et al.
patent: 4989243 (1991-01-01), Choi
patent: 5133006 (1992-07-01), Khuat

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