This circuit transforms 0 and 6 V signals into -4 to 10 V signals and can be used in a shield. The circuit uses transistors that are still common today.
Today we have more compact solutions. This is from a Radio Electronics magazine from October 1990....
This filter was found in Texas Instruments documentation from the 1980s. The circuit uses a common...
16 commercial test circuit for tubes and transistors appeared in Radio Electronics magazine in...