Found in a 1980s American documentation, this circuit can use a SCR and a general-purpose transistor. R2 is 1 M and R1 is 10k. The capacitor is 47 uF.
This circuit for car engine spot adjustment was found in an 80's Radio Electronics. The circuit...
This circuit triggers a relay when it gets dark, thus enabling the lighting of fluorescent lamps, which...
This circuit that generates signals between 1.5 and 2 kHz was found in a documentation from the...