This variable frequency (VFO) oscillator was found in a Japanese publication of 1962. Coil details (in Japanese, but can be deduced) are next to the diagram covering the 3.5 MHz band.
This circuit can be used as a shield for the control of stepper motors from microcontrollers. The...
This circuit was found in a 1960s Motorola documentation. Transistors are types of the time and...
In the figure we have two possible configurations for multivibrators with relay. The idea comes...