Found in a 1969 British publication, this circuit uses a regenerative switch with two transistors to produce pulses that depend on C1. The relay must be in accordance with the supply voltage.
A circuit for controlling the temperature of a heating element was found in a Mullard transistor manual...
We found this circuit in a 1992 Popular Electronics. The circuit has an optical sensor with LED...
I found this circuit in an old English magazine from 1979, but it can be easily assembled with...