This special effect doorbell circuit was found in the January 1984 issue of Radio Electronics magazine. The components are quite common and transistors such as the BC548 and BC558 can be used.
We obtained this circuit from an old Argentine magazine. The circuit originally uses germanium...
We found this circuit in an old English publication. The sensor is a common LDR. and the...
This circuit is from an 80's component manual. The components are from the time, but the circuit...