This circuit is from General Electric from the 80s, using a relay with high current contacts (20 A). The transistor admits equivalent, and any phototransistor can be used as a sensor.
This circuit was found in the Linear Technology Applications of 1997. The circuit uses components from...
This is a 5 V power supply from 2002 documentation, suitable for walkmans and diskmans, common at the...
In fact, this 1967 Electronic Design circuit generates two symmetrical ramps whose frequency...