This circuit was found in the August 1971 Radio Electronics magazine. The SCR admits equivalents and instead of the buzzer a sensitive relay can be used.
Frequency and active cycle of this circuit are fixed by the two crystals that may have different...
We found this circuit in an English documentation. The circuit is current, being the transformer used 9 V...
We found this symmetrical power supply circuit in an Electronics Now magazine from August 1998. The...