Abstract: Transistor switching means in which a principal transistor (T.sub.5) feeds into a load (R.sub.c) when a control signal saturates a control transistor (T.sub.1), a resistance bridge (R.sub.3,R.sub.4) fed by a source (V.sub.AL) then polarizing the base of the principal transistor (T.sub.5).An auxiliary transistor (T.sub.3 a) has its base coupled to the collector of the transistor (T.sub.5) by means of a diode (D.sub.2 a) and one of the two polarization resistances (R.sub.10 -R.sub.11). When the collector-emitter voltage of the principal transistor becomes too strong as a result of a short-circuit in the load, the auxiliary transistor (T.sub.3 a) is saturated and blocks the principal transistor (T.sub.5).Application to detectors of the type having an electro-luminescent diode excited by pulses; these pulses, applied to the auxiliary transistor (T.sub.3 a) block it momentarily in order to ensure the re-setting of the circuit when the overload has disappeared.