This circuit is suitable for the calibration of old analog oscilloscopes. It was found in documentation from the 1970s and could be useful if someone is recovering an oscilloscope of the time.
This circuit was found in a 90s Hands-on Electronics. The transistor can be a BC548. What it does...
This circuit separates the bass from the treble in an audio signal. The circuit is from a Hands On...
The frequency of the signal produced by this circuit depends on the temperature of the diode used...