This circuit automatically turns off small battery-powered devices after a certain amount of time, saving battery life. We found it in a Popular Electronics from the 90s.
The figure shows how to connect a relay to obtain the latch effect. The circuit is from an...
We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of...
This circuit was found in RCA documentation from the 90s. It consists of a power control for a...