Abstract: A microfiche reader provided with a keyboard of the type comprising a radiation emitter such as an infrared radiation emitter, each key being associated with an emitter modulation code and the modulated signal being detected by a photoreceiver. A microcomputer serves to decode the signal delivered by the photodetector and to generate suitable electrical signals for controlling drive motors which initiate the displacements of a microfiche support plate.

Abstract: A respective microcomputer is provided for each processing channel in a data processing system constructed according to safety principles. The information to be output to the process are determined by both microcomputers and are supplied in pairs to two non-fail-safe comparators which drive respective AND gates. Each of the AND gates drives a respective amplifier. The power supply of one amplifier occurs from a battery or the like and the power supply of the other amplifier occurs by transformer-coupled output signals of the first amplifier, which signals are then rectified. The information required for the process are coupled via at least one further amplifier whose power supply is provided by a transformer-coupled and rectified output signal of the second amplifier. Given a signal discrepancy between the two microcomputers, information is not permitted to the process which could lead to a dangerous situation.