This old voice circuit suitable for telephones of the time was found in a Radio Electronics from September 1973. The circuit is powered by a voltage of 7 V.
We found this circuit in an American publication from the 90s. The power must be 2 V more than the...
Found in old American documentation, this circuit makes use of operational amplifiers from the 70s...
This linear LED scale circuit was found in the February 1992 issue of Radio Electronics magazine. Note...