This circuit is from an American documentation from 1975. The circuit uses components of the time which can be replaced by modern equivalents. The coupler is homemade with a lamp and a photocell.
Found in an older Radio Electronics, this circuit generates signals that can be used with regular...
This circuit was obtained in a manual of operational amplifiers of 1973. The circuit uses...
This is a battery powered 3W power amplifier using germanium transistors. The circuit is from an...