Electrical audio signal processing systems and devices – Feedback suppression
Reexamination Certificate
2006-04-11
2006-04-11
Chin, Vivian (Department: 2644)
Electrical audio signal processing systems and devices
Feedback suppression
C381S083000, C379S388020
Reexamination Certificate
active
07027604
ABSTRACT:
This invention includes a circuit for the prevention of acoustic feedback between an electronic device and an audio accessory. In a preferred embodiment, the circuit prevents audio feedback between a cellular telephone and a speakerphone accessory. The circuit includes a current limiting device coupled serially in the receive (Rx) line. The current limiting device is actuated via a delay circuit coupled between the current limiting device and the transmit (Tx) line. When a bias current is presented to the Tx line, the bias propagates through the delay circuit, thereby actuating the current limiting device a predetermined time after the presentation of the bias. The circuit keeps the Rx line open long enough for the phone to deactivate its internal microphone.
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Annamalai Macwien Krishnamurthi
Geren Michael D.
Patil Ashok Ramakant
Soo Kee Eng
Chin Vivian
Faulk Devona E
Motorola Inc.
Watanabe Hisashi D.
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