This very simple circuit uses a phototransistor and a very sensitive relay (reed type) being used over short distances with a lens system. The circuit is from a 1967 Japanese publication.
This circuit was found in Sprague Electric documentation from the 90s. The circuit uses a...
Based on ON Semiconductor's CAT5113, this circuit has the additional purpose of gaining test and...
The emitter of this circuit from a 1995 publication is an infrared LED and the sensors are...