Found in a 90s documentation, this circuit makes use of D1, a switching diode that is uncommon today. D3 is an LED. The circuit monitors 12 V batteries.
This circuit encodes the two channel signals from an amplifier for a multiplex-stereo...
This radio for the medium wave band was found in an old American documentation. The transistors are made...
This lock-up alarm circuit was found in a 1990s Radio Electronics magazine. The sensors are...