General Electric suggests this circuit in a 1980s documentation. The operational of the time is FET-type input. Modern equivalents may be used.
This circuit activates a relay when the water reaches the sensors. The circuit is from a Radio...
The purpose of this PLL circuit that we found in the November 1986 Radio Electronics magazine is...
This increased voltage regulator is from a 1980 publication, but it can be mounted using a BD136...