This circuit was found in an American documentation from the 80's. The sensor is a special integrated circuit, uncommon in our times. There are modern equivalents.
The circuit in the figure trips with a negative transition of the input signal, its output...
The basic frequency of this circuit is determined by the capacitor of 470 nF and the adjustment of the...
The load current can be adjusted up to about 1 A. The transistor can be TIP32 or TIP42. The...