Abstract: An industrial control, communication and information system in which a speech synthesis device produces an analog speech waveform from digital data stored in a memory under control of a microprocessing unit and is interfaced to a source of control or speech selection signals by an interface system. The interface system uses the input switch closure to generate a signal to switch on power to the logic and other electronic circuits and protects the internal logic from harsh external electrical conditions such as transients and the like and eliminates false inputs and the effects of switch bounce.