Hands-free telephone

Details Hands-free telephone Hands-free telephone

1989-02-21

1991-01-01

Ng, Jin F.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379388, 379 58, H04M 908

Patent

active

049824252

ABSTRACT:
In order to perform voice-switched telephoning, a hands-free telephone includes a speaker, a microphone, a receive variable attenuator (R-ATT), a transmit variable attenuator (T-ATT), a receive signal detector, a transmit signal detector and an attenuation control circuit. The telephone also includes an auxiliary control circuit which prevents the output of the transmit signal detector from reaching the attenuation control circuit during a transient period between a call origination and the beginning of a conversation. During the transient period, only the speaker is enabled to output a ringback tone therethrough. When the output level of the transmit signal detector exceeds a predetermined level, the auxiliary control circuit passes the output of the transmit signal detector to the attenuation control circuit to start the voice-switched telephoning. Once the auxiliary control circuit passes the output of the transmit signal detector, it holds this state until the conversation finishes.

REFERENCES:
patent: 4731811 (1988-03-01), Dubus
patent: 4737976 (1988-04-01), Borth et al.

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