This circuit with current up to 100 mA according to the transformer was found in the Radio Electronics magazine of October 1991. The regulation is done directly by the zeners.
The frequency of this oscillator depends on the crystal used. The transistors are general purpose. We...
The circuit shown in the figure serves as a pre-amplifier with a voltage gain of around 12 times,...
Found in a 1964 Philips manual, this circuit uses only passive components. The relay is a high...