This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
The circuit presented is from the Linear Applications Handbook of the National Semiconductor of...
This timer counts down the times until, at the end, it activates a relay. The programming time is...
This power control with SCR was found in Radio Electronics from April 1966. The components are...