Click to expand full text
UNISONIC TECHNOLOGIES CO., LTD
U4082B
LINEAR INTEGRATED CIRCUIT
VOICE SWITCHED SPEAKER-PHONE CIRCUIT
DESCRIPTION
As a voice switched speaker-phone integrated circuit, the UTC U4082B includes the necessary amplifiers, attenuators, level detectors and control algorithm.
To form the UTC U4082B’s internal circuit, there is an internal microphone amplifier with adjustable gain and mute control, internal transmit and Receive attenuators (operate in a complementary manner), level detectors at both input and output of both attenuators, and background noise monitors for both the transmit and receive channels.
The dial tone can be pretended from being attenuated by the receive background noise monitor circuit by a dial tone detector.