This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V batteries since it requires a symmetrical source.
The Texas Instruments LM5178 Buck-boost controller is capable of operating in the 4.2 to 55 V (60...
This 1970 Philips circuit uses a mechanical counter. The circuit is triggered by a reed switch...
This 1 MHz oscillator was found in an Electronics World of 1969. The circuit uses a...