PBL38813

The PBL 388 13 contains all the necessary circuitry, amplifiers, detectors, comparator and control functions to implement a high performance, voice-switched, loudspeaking, "hands-free " telephone. The gain dynamics of PBL38813 (attenuation between channels) is selectable (25dB or 50dB) via a separate pin. A background noise detector in the transmitting channel reduces the influence of continuous external noise signals to the switching .

The PBL 388 13 is designed for telephone systems that are either powered from the telephone line or from a mains powered constant voltage dc. supply. The circuit contains a transformerless audio power amplifier PBL38813 with a current supply circuitry (patented) that eliminates the need of inductors. Automatic volume attenuation in the power amplifier extends the operating range at low line currents. A special feature in PBL38813 is that the power amplifier volume control can be implemented either as an ac. potentiometer control or as a digital control by a m-processor (dc. control).

Filtering is possible of both, the audio and the speech switching control signals, in both transmitter of PBL38813 and receiver channels.