Found in a 1967 American publication, this circuit with feedback for two transistors has a gain of 20 times. Phototransistors are types of the time.
This amplifier can be powered with voltages between 2 and 5 V with power up to 100 mW. The minimum...
In the figure we have the way to control a TIC series triac with a reed switch. The current in the...
This practical idea from a 1992 documentation shows how to count the turns of a winder using a...