Found in American documentation from the 90s, this circuit can measure frequencies on a linear scale from 0 to 1 kHz. The components can be changed to measure other ranges.
This simple circuit for motors that depends on the MOSFET used was found in the January 1998...
This transistorized shield also functions as a logic gate. The power supply can be in the range of 4.5...
Found in a 90s Popular Electronics, this Hartley oscillator uses an output transformer of the type...