This 1974 circuit uses two 555 integrated circuits in a very traditional configuration. The circuit can be powered by voltages from 9 to 12 V and for greater volume an amplifier stage can be added.
This voltage-controlled oscillator or VCO has rectangular and triangular signal outputs. The...
This circuit was obtained from a 1965 Radio Electronics. The semiconductors used admit modern...
This Hall sensor circuit is intended to isolate an audio signal applied through a coil. The...