Simplified truck tractor socket wiring

A power distribution unit useful in a truck tractor to apply electrical power to a selected one or more of a plurality of signal terminals of a tractor-mounted connector in a tractor-to-trailer electrical connection. The power distribution unit comprises a power bus adapted for connection to a power source, an output terminal corresponding to each signal terminal of the connector, a switch connected between each output terminal and the power bus, and an actuator associated with each switch and operable upon receipt of a respective control signal to operate the associated switch.