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 alarm circuit was found in a 1982 publication. It uses components that can still be found...
This circuit was found in an American publication in 1966. The circuit uses a general-purpose FET that...
Found in an Elektor from the 90s, this circuit converts signals from the 280 kHz band to 516 kHz,...