Abstract: Adapter for field signals of computers, microprocessors systems or the like digital electronic circuits. The adapter receives either AC or DC signals, from external or field sources or from computers, microprocessor systems of the like digital electronic circuits, and provides AC or DC control voltages to external or field controls or to computers, microprocessor systems or the like digital electronic circuits. The adapter includes a first switching circuit which responds to the level of an input signal, and which actuates an oscillator which includes the primary of a transformer as its load. Energy is transferred by the transformer secondary to appropriate control circuits for use elsewhere. The adapter also includes a second switching circuit which also responds to a different level of the input signal, the second switching circuit diverting the input signal current into itself across an artificial load when the first switching circuit is inoperative.