Freeze Alarm (CB14454E)

The circuit of a 1968 publication can be implemented with more modern transistors such as BC548 for NPN and BC558 for PNP.

Divider by N with the 4017 (2) (CB12131E)
With this circuit it is possible to divide the frequency of a rectangular signal by values between 2...
FM Noise Filter (CB19285E)
This circuit, which we find in a documentation from the 70s, filters out the Ru [occurring in...
Phone Bell (CB18151E)
This circuit simulates the call tone of a telephone. The transducer is a high impedance capsule, and...