This paper presents a CMOS mixed-signal MODEM ASIC for data transmission on the low-voltage power line. The circuit includes all the analog circuitry needed for input interfacing and modulation/demodulation (PLL-based frequency synthesis, slave filter
banks with PLL master VCO for tuning, and decision circuitry) plus the logic circuitry needed for control purposes. To allow the communication between the electrical household appliances and a remote unit to control them as well as to reduce the cost, an unique
mixed-signal ASIC, made of two parts, one operating at high frequencies and another operating at lower frequencies, has been designed. The High Frequencies Module must allow the connection with the external control systems and, to ensure reasonable robustness, has to be able to send and receive signals using at least two
different channels (to avoid local and temporary degradations of the communication). The Low Frequencies Module is needed to manage the indoors communication. This module enables the transmission of signals within distances between 50 and 100 meters with a speed
in the order of, but never less than, 100 bits/s. This link should be accomplished by using a frequency range in such a way that a maximum number of channels are disposable to allow the control of as many different in-house devices as possible. Again, to this end, two
different tunable channels have to be simultaneously available: one to control the quality of the signal and the other to allow the effective communication.