Abstract: A home automation module having an externally powered communications port. The module includes an automation microprocessor for controlling the module, a communications port for enabling the module to draw power in limited quantities from an external source, a receiver/transmitter section, a power line carrier (PLC) coupler for enabling the transfer of signals between the module and a main while electrically isolating the module from the main, a zero-crossing detector for monitoring the phase of the power on the main while maintaining substantial electrical isolation of the module from the main, and a boost regulator for enabling the module to derive sufficient power from the communications port to drive the PLC coupler during signal transmissions from the module to the main. The detector maintains substantial electrical isolation through an opto-isolator. The boost regulator stores up power over time so that sufficient power will be available when the demand is made.