DESCRIPTION
The Contek 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.

FEATURES
* Improved attenuator gain range: 52dB between Transmit and Receive
* Low voltage operation for line-powered applications(3~6.5V)
* 4-point signal sensing for improved sensitivity
* Background noise monitors for both Transmit and Receive paths
* Microphone amplifier gain set by external Resistors-Mute function included
* Chip disable for active/standby operation
* On board filter pinned-out for user defined function
* Dial tone detector to inhibit receive idle mode during dial tone presence