Found in the American 73 magazine for radio amateurs, this circuit can test common quartz crystals. The circuit includes the power supply.
This low-pass circuit was found in the December 1990 issue of Radio Electronics magazine. The...
We find this simple musical instrument in a 1977 Radio Shack documentation. The key resistors must be...
Suggested by a Philips documentation from 1970, this circuit uses period components, operating at 50...