This circuit was obtained from Dutch documentation from 1967. It uses transistors of the time which can be the BFY50 and 51 for the output and the BC series for the others.
This circuit for a digital module was found in the September 1989 Radio Electronics magazine. The...
This 1970 Philips circuit uses a mechanical counter. The circuit is triggered by a reed switch...
We found this circuit in an old Mullard (Philips) documentation. The sensor consists of a...