This low frequency divider uses unijunction transistors. The bipolar transistor can be a BC548 and the zener diode Z4XL can be a 12 V zener. The circuit was found in a 1967 publication.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...