Found in a 1980s American documentation, this circuit uses programmable unijunction transistors of the time. The time interval obtained depends on the capacitors that can be changed.
This circuit is from a 1976 Motorola CMOS manual. It can be implemented with modern Darlingtons like...
In the figure we have the way of modulating or controlling the frequency of a relaxation...
The purpose of this circuit is to monitor the operation of an alternator in cars with a 12 V...