The ST7540 is a Half Duplex synchronous/asynchronous FSK Modem designed for power line communication network applications. It operates from a single supply voltage and integrates a line driver and two linear regulators for 5V and 3.3V. The device operation is controlled by means of an internal register, programmable through the synchronous serial interface. Additional functions as watchdog, clock output, output voltage and current control, preamble detection, time-out and band in use are included. Realized in Multipower BCD5 technology that allows to integrate DMOS, Bipolar and CMOS structures in the same chip.