This blocking oscillator configuration was found in a 1964 American book. The circuit can be designed with modern transistors and the frequency depends on the transformer.
This circuit was obtained from an 80s factory manual. The integrated circuits used are uncommon...
We found this circuit in a 1991s PE Hobbyst Handbook. The circuit fires 10 LEDs that can control...
This circuit is from a 1984 magazine, but it can be assembled with a BC558 for TR1, BC548 for TR2...