UTC MC34118

The UTC MC34118 voice switched speaker-phone integrated circuit incorporates the necessary amplifiers, attenuators, level detectors and control algorithm to form the heart of a high quality hands-free speaker-phone system. It includes a microphone amplifier with adjustable gain and mute control. Transmit and Receive attenuators which 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. A dial tone detector prevents the dial tone from being attenuated by the receive background noise monitor circuit. Also two line driver amplifiers which can be used to form a hybrid network in conjunction with an external coupling transformer. A high-pass filter can be used to filter out 60Hz noise in the receive channel, or for other filtering functions. A chip disable pin permits powers down the entire circuit to converse power on long loops where loop current is at a minimum. The UTC MC34118 may be operated from a power supply, or it can be powered from the telephone line, requiring typically 5mA. The UTC MC34118 can be interfaced directly to TIP and RING( through a coupling transformer) for stand-alone operation, or it can be used in conjunction with a handset speech network and/or other features of a feature phone.