This simple timer with unijunction transistor was found in an old American technical documentation. We can use 2N2646 for the unijunction and BC548 for the transistor.
Employing transistors of the time, this circuit was found in a documentation from 1963. The coils...
This circuit with the CK722 was found in a Raytheon publication from the 60's. The relay is of the...
This circuit is from a 1975 amateur radio manual. The components can be approximated to the...