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.

Simple MW Radio 2 (CB4360E)
Originally this circuit is from an English magazine, but I found it in Argentina's Radio Chassis...
Current limiter (CB25534E)
This circuit was found in the December 1992 Radio Electronis magazine. R2 is an NTC, there is a...
Signal Follower (CB1356E )
If you have a common analog multimeter, you can increase its input resistance in the measurement of...