This circuit was found in a 90's Electronic Design. The circuit can be adapted to use modern components. The power supply is made with 5 V which allows its use as a shield sensor.
This circuit detects a light window using two operating systems. The circuit is from a July 1992...
This circuit was found in an American documentation from 1966. The transistors are from that time...
This low-power intercom can be powered by solar cells. The circuit is two-way, with an integrated of the...