This optoelectronic, finger-operated keyboard for use in industrial measurement equipment is designed to achieve an optimum signal-to-noise ratio and minimize the drop in the intensity of the infrared emitters during the service life of the measurement equipment. The keys for generating respective associated operation signals (n1, n2, n3) have an infrared-transmitting cover (1), one infrared emitter (3) per key disposed at the inside (12) of the cover and emitting light collimated virtually perpendicular thereto, one infrared detector (4) adjacent to each infrared emitter which is separated from the latter by a shield (5) opaque to infrared and is pointed at the cover, said infrared detector being located within the main radiation range of the infrared light emitted by the infrared emitter and scattered at a finger (2) but outside the infrared light reflected from the outside and/or inside of the cover. An operating circuit (8) comprises a separate control and detection circuit (15, 25, 35) for each key which generates current-control pulses (si1, si2, si3) with a mark/space ratio less than 1:1 for feeding the infrared emitter (13, 23, 33), and a scanning circuit (18) common to all keys which switches a current switch (19) connecting all control and detection circuits (15, 25, 35) to one terminal (SN) of a supply-voltage source into a conducting state.
