A control circuit including at least one switch and a plurality of rectifiers for selectively applying a-c utility power to either or both of two remote electrically-powered apparatus at respective first and second states of rectification by means of a conventional two-wire interconnection cable. Where one of the apparatus is of a type, such as a motor, adapted to be powered by a full-wave a-c, the control circuit includes a relay and relay switch responsive to switch-selectable half-wave a-c for connecting the motor to receive full-wave power. In one disclosed embodiment, the two apparatus comprise a composite smoke detector and lamp fixture, and the control circuit provides continuous power at a first state of rectification to the smoke detector portion of the fixture and switch-selectable power at a second state of rectification to the fixture lamp.