This circuit was obtained from an Electronics Design of 1964. The circuit makes use of tunnel diodes that are uncommon today. The circuit works with very weak signals.
In the waiting condition, the consumption of this alarm is extremely low, of the order of...
This is a project from a 1987 publication. The circuit tests transistors without removing them...
This sensitive motion sensor with inductive sensor was found in a 90s Elektor. The circuit uses only...