Print wheel control

A control system for operating a single high-speed print wheel is disclosed. The control system includes a print wheel drive motor having a coded disc with transparent portions forming a four-level Gray code for indicating the position of the print wheel. An optical and electronic system is used for positioning the print wheel and also for the purpose of providing an electronic detent which uses the motive power of the print wheel drive for holding the print wheel in selected printing positions. A similar optical and electronic system is used for controlling a paper advance mechanism. The disclosed system also includes a print hammer with a voice coil type drive to permit positive, bidirectional hammer control.