Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
This configuration was found in the January 1992 Radio Electronics magazine. The frequency is set...
Using a zener diode it is possible to change the linearity of the scale of an analog instrument by...
This circuit uses a common multimeter on the voltage scale to measure the beta gain of a...