The diagram shows a tone control with the LM381 IC. The circuit is from a Radio Electronics from February 1990. The power supply is single.
This reinforcing stages from a 1960s documentation. No information is given about the transformer...
This 2003 circuit uses two types of sensors: by reed-switch and by infrared. If the magnetic...
Indicated for frequency measurements, this circuit can operate with inputs up to 1 MHz. We found...