This circuit was obtained from an American 1980s documentation. The frequency depends on the crystal and the circuit may be a PNP that reaches the generated frequency.
This circuit can generate signals from 80 to 800 Hz with an amplitude of 0.3 V. We find it in a...
We found this circuit in a Hands-On Electroncs from the 90s. The circuit uses an LED indicator. Diodes...
We found this configuration in a documentation for radio amateurs from 1974. The circuit can be...