U4055B

U4055B/U4055B1 Low-Voltage Electronic Speech Circuit with Dialer Interface Description The U4055B electronic speech circuit is a linear integrated circuit for use in telephone and other line fed terminal equipment. It replaces the common speech circuit with carbon microphone, hybrid transformer, sidetone equivalent and ear protection rectifiers. A low-cost electrodynamic transducer is used as the earphone. It contains all components necessary for amplification of signals and adaption to the line. Features www.DataSheet4U.com D An electronic circuit replaces the microphone hybrid transformer D Symmetrical input for dynamic or piezo microphone D High performance through the use of dynamic transducers as the earphone (non-linear distortion 2 %) D DTMF interface with muting D Supply voltage for dialer D High range of line feeding current D Input resistance independent of line current and sidetone suppression circuit. D Built-in ear protection by earphone voltage limiter D Operation possible from 8 mA x D Automatic line loss compensation U4055B1: High level mute; U4055B: Low level mute Figure 1. Block diagram and pin connection TELEFUNKEN Semiconductors Rev. A1, 06-May-96 1 (10) Preliminary Information U4055B/U4055B1 Pin Description Pin 1, 2 Symbol Function H1 and H2 The push-pull complementary outputs of the receive amplifier. Dynamic transducers with a minimum impedance of 100 W can be directly driven by these outputs. GND Ground. ST The output of the sidetone cancella...