generating clock frequency of the second counter 22 are also supplied the second counter 22 is incremented while the heating resistance 2 is supplied and carries out the addition of the supply times of said resistance the second counter 22 emits an end of cycle signal on its outlet path s 2 via a resistance 19 as soon as it has carried out a counting operation of a duration greater than a predetermined time t 2 this end of cycle signal is directed toward the zero set path r 2 of the second counter 22 and in parallel to the zero set path r 1 of the first counter 21 if the first counter 21 has carried out a counting operation of a duration greater than a predetermined time t 1 without having received a zero set signal on its reception path r 1 it emits on its outlet path s 1 a signal to the relay 20 which opens the supply circuit of the heating resistance this cutoff signal also effecting via the first transistor 16 the blocking of the clock frequency generating means of the first counter rearmament means 23 are provided to permit the user to turn on the iron again and to restart the safety system when the latter has cut off the supply of the heating resistance following the detection of a prolonged non use condition these re arming means 23 when they are actuated by the user emit an impulse on the zero set paths r 1 r 2 of the first and second.