This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
This circuit was found in Philips documentation from 1967. The components are of the time, being...
The Variable Frequency Oscillator (VFO) shown in the figure can generate signals in a frequency...
This circuit uses an operational amplifier to modulate the light emitted by an LED with audio...