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.
This circuit mutes a system when a phone call is received. The circuit is from a Radio Electronics from...
This circuit is from a 1967 publication. The configuration holds true for modern transistors having...
L1 is the secunday wound of a common power transformer with voltages between 6 and 12 V and...