FIELD: signalling systems. SUBSTANCE: system has two posts 1 and 2, onto which two pairs of irradiators 3,4 and 5,6 are mounted correspondingly, photodetectors 7 and 8, amplifiers 9, 10, sync rectifiers 11, 12, master oscillator 13, second frequency former 14, power regulators 15, 16, threshold units 17-20, OR gates 21-23, signalling units 24. Moreover, unit has two integrators 25, 26, switches 27, 28, holding units 29. When object appears in control zone of one or the other set, light flux balance changes in photodetectors 7 and 8, as well as signal from sync detectors 11, 12 and one threshold unit from threshold units 17-20 operates. Signaling unit 24 turns on through OR gates 21-23. EFFECT: improved functional capability. 5 cl, 6 dwg
