Neon Fuse Blown Monitor (CB24104E)

This circuit was found in the January 1971 Radio Electronics magazine. It keeps the light flashing if the fuse blows.

Mini Central for Intercoms (CB18747E)
In fact, we can say that this circuit found in documentation from the 90s, consists of an intercom...
Digital Multimeter (CB4477E)
The basic integrated circuits of this 1988 multimeter are no longer very common today, but if...
Microphone Preamplifie (CB1404E)
This circuit is from an old publication of the 70's. It can be implemented with modern transistors like the...