Hands-free, voice switched, SOP-28

The TS34118 Voice Hands-Free circuitry includes the necessary amplifiers, attenuators, level detectors and a control algorithm that is at the heart
A high-quality hands-free system. The circuit includes a microphone amplifier with adjustable gain and MUTE control, complementary transmit and receive attenuators, level detectors at the input and output of both attenuators, and background noise monitors for the transmit and receive channels. A dial tone detector prevents the dial from being attenuated by the background noise monitoring circuit on reception. Also included are two line drive amplifiers that can 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 allows the entire circuit to be switched off to save energy during long loops where the loop current is minimal.
The TS34118 can be powered by a power supply or telephone line and typically requires 5.0 mA. The TS34118 can be connected directly to the tip and ring (via a coupling transformer) for stand-alone operation, or it can
Can be used in conjunction with a handset voice network and/or other functions of a function telephone.

Key features