This anti-theft circuit was found in a 1985 documentation. It uses common components that can still be found easily. The relay is 12 V and the circuit has timings of 3 minutes and 20 seconds.
This circuit, when triggered, locks, and remains so until the source is switched off for a moment or...
This buzzer trigger can be used for small alarms. We find it in an 80’s American documentation. The...
This relay without lock uses a general-purpose transistor. The relay is according to the supply....