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 battery-powered micropower supply was shown in Radio Electronics magazine in 1991. The...
Found in a 1965 Electronic Design, this circuit can be made with modern equivalent transistors. The...
In this circuit, the current in solenoid X1 can be adjusted and its intensity measured to the...