Found in 1967 General Electric documentation this circuit appears elsewhere in this section. SCRs are common to the 106 Series and more steps can be added to the circuit.
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...