This circuit was found in a Philips documentation from 1970. The components are of the time, difficult to find today, but the configuration can be adapted to use modern equivalent components.
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...