This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V batteries since it requires a symmetrical source.
Found in a November 1977 Radio Electronics magazine, this digital circuit was described in an...
This circuit is from a manual of linear integrated circuits of the 80s. The operational is of the...
The tone generated by this bell changes when we press and release the switch. The circuit is from...