This circuit was found in a publication by Edelman from 1924. The power comes from the battery and the listening is through a high-impedance headphone.
This VCO makes use of an RC4558 which is an operational amplifier with characteristics close to...
In the figure we have a symmetrical power supply stabilized by a zener diode. Transformer and...
The crystal used in this oscillator can have frequencies up to 30 MHz or more, depending on the...