This circuit can be used to test crystals from 1 to 20 MHz and also has an output to measure their frequency. We found it in the November 1998 Electronics Now magazine.
This headphone amplifier using a pickup coil can be used as an extension for devices such as TVs,...
This circuit uses common components activating a control relay for the water pumps. The sensors are...
We found this circuit in a 1967 El3ectronics World. The transistors are from the era but can be...