This control for 12 V drills was found in a 90s Elektor. The components are current, and Q1 can be replaced by a TIP42 mounted on a heat radiator.
This squelch is activated by its own noise, acting automatically. It is used in communications...
This was one of the National Semiconductor clock modules very popular in the 70s and 80s. In the...
We found this circuit in an old Radio Electronics. The transistors can be the BC548. The circuit...