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.
Found in a Popular Electronics from the 90s, this circuit operates up to about 5 MHz input....
This circuit was found in a 1987 edition of the United States' Hands-On Electronics magazine. The...
This circuit that uses potentiometer tuning, was found in a documentation from the 80's. The...