An electric circuit is provided with a single jack for connection to either a first remote powered device via a first plug or a second remote unpowered device via a second plug. A power requirement detection circuit is provided for generating a control signal representing whether the connected plug is the first plug or the second plug. A normally deactivated switch is connected between the power source and the jack and is operable to supply power to the jack when activated. A switch activation circuit is responsive to the control signal for actuating the switch when the first plug is connected.
