This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
This circuit emits a warning sound when night falls. The circuit is from a Hands On Electronics from...
This circuit is from an April 2000 Poptronics. The magazine no longer exists, but the circuit can...
This separator filter is from an old publication. The capacitor can have 10 to 47 uF of the...