This circuit was found in a Popular Electronics from the 90's. The transistors are general-purpose types and the loaded load depends on the voltage and must have a maximum current of 100 mA.
This simple circuit that activates a buzzer was found in the July 1971 Radio Electronics magazine. The...
This two-band receiver capable of tuning medium waves and the 3.5 to 10 MHz band was sold in Japan...
We found this circuit in an English documentation from 1995. With it it is possible to measure a...