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.
We found this circuit in an Electronics Handbook from the 1980s. It filters out noise from a radio...
We found this circuit in the May 1989 issue of Radio Electronics magazine. The circuit uses...
This TTL circuit generates a 100 MHz signal for digital instruments. The CI is not easy to obtain,...