Abstract: An apparatus for providing power to electronic equipment having multiple power sources. The separate and distinct power sources drive corresponding primary circuits such that the power source inputs can be of a different nature and the power supply can be designed to accommodate different types of voltage inputs. Each primary circuit is isolated one from the other, such that damage resulting from ground-loop potentials is minimized by circuit isolation. Circuit isolation is accomplished by optical isolation between each primary circuit.

Abstract: A modem (106) is arranged with a power control circuit (113) for controlling the power flow to the modem, based on the modem's data activity. After initial data activity is established (303), the power control circuit monitors the modem to determine when the data activity ceases. When the power control circuit determines that modem activity is no longer present (305), it releases a power-control relay (114), thus powering-down the modem (307). The power control circuit then continues to monitor the modem to determine when data activity returns. When the power control circuit determines that modem activity has returned (309), it operates the power-control relay, thus powering-up the modem (311). Normal data activity now continues (313).