This circuit is based on the light comparison of two LDR sensors. We found it in a 90s Popular Electronics. The transistor must be according to the indicator or load being driven.
We found this circuit in a 1969 General Electric documentation. The circuit uses transistors of the...
This circuit opens a reservoir when it starts to rain and closes it when the humidity sensor...
With this circuit it is possible to use a control voltage to select audio signals that pass...