Address decoder using the 74LS138 (CB20537E)

This decoder circuit 3 of 8 was found in a publication for PCs from 1992. The circuits are TTL and must be powered with 5 V.

Delayed SCR trigger (CB19336E)
The circuit shown is from an old European publication. In it we have the way to activate a relay...
Audio Line Amplifier (CB4769E)
We found this circuit in a European publication from the 1990s. Transistors are still common types...
Active three-tone filter (CB20808E)
This circuit was found in an American documentation and can be added to common amplifiers of any...