This circuit for old analog telephones is from period documentation. It controls a relay that can be used to turn the extension on and off.
In the figure the well-known basic configuration of relaxation oscillator with unijunction...
This circuit turns on the relay 12 seconds after S1 is closed. The time is given by C1. The...
We found this circuit in a 1964 Electronic Design. The triac and SCR can be replaced with modern...