This circuit is from an American publication of the 80's. It makes use of components of the time. However, the circuit is the basis for a modern shield application since the input is TTL.
We found this logic level indicator in a 1976 amateur radio documentation. The circuit is powered by...
This 6-transistor transistor radio is a RCA product from the 1960s. The circuit is powered by a 9...
The operational amplifier is old. The circuit is from an 80's documentation but can be designed...