We found this circuit in a Radio Electronics magazine from November 1976. The clock frequency is divided by 10 and the maximum value depends on the integrated circuits used.
This circuit is from old European documentation. R1 depends on the output voltage of the...
This SCR circuit activates a buzzer when triggered. The circuit is from a Popular Electronics from...
This 130 V drive uses an integrated circuit not very easy to find, which is the LM143. The circuit is...