Found in an Electronic Design from the 90's, this circuit indicates three voltage levels by activating the LED in 3 modes: off, flashing and on for high voltage.
This circuit that can only be used with simple resistive and inductive loads (never electronic) was...
This digital instrument input circuit was found in the September 1989 issue of Radio Electronics...
This circuit was found in an 80s documentation. The integrated circuit used is from that time,...