Published in a PE Hobbyst Handbook of 1991, this sensor uses an integrated circuit that is unusual today. The circuit is based on a high frequency oscillator.
This low frequency oscillator with an operational amplifier of type 741 has adjustment of the mark...
This circuit was found in a Popular Electronics from the 90s. Transistors are general purpose...
The AT21CS11 memory device offers an extended voltage range to accommodate lithium-ion battery...