This rain, flood or leak sensor was found in a 90s Popular Electronics. All the components used are common today. The transistor can be the BC548.
September 2017 - Mouser Electronics is supplying the entire line of high power MCx resistors from...
March 2017 - The new Texas Dual ISO762xxL digital isolators are available at Mouser Electronics...
Found in 1980s documentation, this circuit uses a small transistor radio output transformer and a double...