These optical relays, which can act as a shield, were found in an American documentation from the 1980s. The circuit has a LDR sensor. It can be adapted for other types of sensors.
This circuit was found in an 80's documentation using an NE5514, operating at the time. The font...
This circuit generates sinusoidal signals between 300 and 3000 Hz. We find a 303 Circuits from the 90's....
This circuit from a 2003 documentation, has a protection system that disarms the power supply if...