We found this circuit in a Poptronics from 1998. The circuit can be extended to more competitors with another 4011. The power can be made with voltages from 6 to 12 V.
This counterphase circuit is from a 1973 publication, and can work with mains voltages or 12 V....
This simple transistor tester was found in a Japanese magazine in 1967. It tests general purpose...
This basic 100 kHz oscillator is suitable for use in calibration. We found it in documentation from the...