Logic level indicator 7400 (CB22407E)

In the figure we have a simple logic level indicator for TTL circuits or powered by 5 V.

Carbon Microphone Preamplifier (CB12905E)
This very old circuit, from a publication from the 1970s, uses a germanium transistor and two...
Touch Switch (CB16091E)
In the figure we have a very sensitive touch switch circuit. A touch of the sensor causes the...
Mini Central for Intercoms (CB18747E)
In fact, we can say that this circuit found in documentation from the 90s, consists of an intercom...