An amorphous silicon position sensitive detector (PSD) has been developed by utilization of uniform wide area photovoltaic generation characteristics. A series of technical data on design rules and performance are firstly presented. Secondly an application to telephone terminal message board system is described.

The telephone terminal equipped with an amorphous silicon position sensitive detector for a keyboard as an input device implemented under a liquid crystal display (LCD) as an output device can transmit not only voice but also graphic information. This is one of the remarkable applications of an amorphous silicon position sensitive detector which makes a telephone a low-cost, easy-to-use and graphic information medium.