This telephone recording circuit was found in the June 1979 issue of Radio Electronics magazine. The components are common at the time and the power is supplied by the power grid.
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...