THE TRUTH REVEALER: this was the nickname given by the Judica-Cordiglia brothers to a piece of test equipment they developed and built in 1960.
The unit was a sophisticated (for its day) notch filter, used to "clean up" the audio signals received from space probes and manned capsules. The unit used a series of capacitors and several self-built copper-wire chokes. The unit could be used both as a band-pass or a band-stop filter and operated in the low and high frequency ranges. A "Geloso" tape recorder was used as the source, with another similar unit being used as the destination device. The audio signals were monitored using a "Chinaglia" brand oscilloscope and could be played back through speakers or headphones. Most of the units used in this device still survive! Apparently, noise-shaping in 1960 required a lot of hard work: but it gave the desired results!