Water activated alarm (CB7993E)

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.

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VCR Amplifier (CB25269E)
This circuit for VCR recording heads was found in the February 1990 issue of Radio Electronics magazine....
Simple continuity tester (CB7955E)
This very simple continuity tester uses a small 1.5 V lamp (type used in flashlights). Can be...
Transistor Radio TR3B (CB18388E)
This commercial radio with 3 earphone listening transistors was manufactured in Japan in the...