This circuit was obtained from an American documentation from the 1980s. The T1 triggering transformer must provide 250 V pulses for the lamp to trigger.
The oscillator shown in the figure keeps its frequency constant in an active cycle adjustment...
For bench use, this circuit functions as a bistable safety switch. The circuit is from a Radio...
In fact, this is the circuit also known as “vox”, that is, a relay triggered by sound. This...