This circuit triggers a relay when a light beam that hits the phototransistor is cut off. The circuit is from Electronics Now and the supply voltage depends on the relay voltage.
This circuit, found in 1980s documentation, produces a rectangular signal of the same frequency as the...
The purpose of this circuit from a 1995 publication. Its purpose is to alert a person when he...
This simple transmitter for the citizen range was obtained in a 1983 publication and has only one...