Single wire concurrent bi-directional communication for power supply unit

A communication system where first and second devices communicate concurrently and bidirectionally over a single wire, in addition to a ground. The second device can be a computing device having a powered component which requires a certain power output, for instance, and the first device may be a power supply unit. The second device provides a signal on a control line (the single wire) which is characterized by a frequency, pulse width, duty cycle and/or an amplitude which is associated with a message from the second device. The first device recognizes the message in the signal and invokes a corresponding function, such as by enabling a corresponding power supply. The power supply provides power to the second device via a separate power line. Further, the first device modifies the signal, without adding power, to provide a message from the first device, concurrent with the message from the second device.