Telephonic communications – Substation or terminal circuitry – For loudspeaking terminal
Patent
1994-12-06
1996-08-06
Hofsass, Jeffrey
Telephonic communications
Substation or terminal circuitry
For loudspeaking terminal
379389, 379388, 379406, H04M 908
Patent
active
055442420
ABSTRACT:
A control circuit for a speakerphone circuit which utilizes an event driven circuit to determine the appropriate gain for the receive and transmit channels is provided. Detectors monitor the relative magnitudes of the signal in the transmit and receive channels. Separate signal-to-noise detectors determine whether signals present in the two channels are voice signals. The event driven circuit receives these inputs, and dependent on the present state (i.e., transmit, receive, or idle) transitions to a new state in accordance with predefined criteria incorporated into the event driven circuit. In particular, the present invention allows a transition in a single step from a receive to a transmit state, without passing through an idle state. Transition or dummy states allow implementation with simple logic and provide hysteresis.
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Exar Corporation
Hofsass Jeffrey
Saint-Surin Jacques M.
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