Code Switch (CB6536E)

We found this circuit in a Popular Electronics of the 80s. Used integrated circuits are uncommon today.

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Carbon Microphone Preamplifier (CB14801E)
Carbon microphones are no longer used in most projects. However, finding one in the scrap metal, it...
Sonic Repellent for Animals (CB13162E)
This circuit produces a strong tone of audio or ultrasound, depending on the values of components C1 and...
Alarm (CB12604E)
This alarm from an old 1978 publication uses PNP transistors and driver and output transformers that are...