Using the 555 and 7400 this circuit was found in the September 1977 Radio Electronics magazine. The power supply must be made with a voltage of 5 V.
In fact, we can say that this circuit found in documentation from the 90s, consists of an intercom...
The basic integrated circuits of this 1988 multimeter are no longer very common today, but if...
This circuit is from an old publication of the 70's. It can be implemented with modern transistors like the...