This timer with two unijunction transistors and one SCR was found in an American documentation from 1964. The unijunction transistors could be the 2N2646.
This circuit, from an old publication from the 1970s, can be made with silicon transistors like...
We find this circuit in documentation from the 1980s. The triac and diac are of conventional types...
The purpose of this circuit is to convert a short-lived pulse into a negative rectangular pulse. The...