Abstract: A system is disclosed which allows the transfer of electric power and data signals between two circuits yet allows the circuits to be electrify isolated from one another. The system comprises a loosely-coupled transformer having first and second windings separated by a sheet of insulating material. In one mode an alternating signal is applied by a first processing circuit to the first winding. An alternating signal is generated in the second winding which is rectified and then used as a power supply. In a second mode, a second processing circuit applies pulses to the second winding. Pulses are induced in the first winding which are amplified and output by the first processing circuit. Suitable first and second processing circuits are disclosed.