Finally, here's one effect with schematics and a manual. This stompbox was made in 1977 in Kazan, USSR. The effect's full name as it appears on the first page of the manual is "Amplifier with level limitation, Booster PR 2.940 019 RE". The manual suggests the Booster should be used with several kinds of electrified musical instruments, s.a. guitar, organ or teremin in order to change the sound's coloring and make it sound more like wind or fiddle instruments (clarinet, saxophone, cello). It also comes with a DIN-5 cord which was a Soviet standard for all electric musical instruments and amplifiers. The booster uses one 9 volt battery.

Here's a couple of words from the pedal' owner:
Booster is classic-looking fuzz pedal. It has two controls - tone and volume. Tone works only in two positions - it should be switch in fact, but it wouldn't look so cool;)
Volume output is rather low. Sound is real nice, my friend called it "organic", I would describe it as "rooty" - nice, old fashioned fuzz a'la Velvet Underground. When I bought Booster, it was not working. My friend, £ukasz, who is expert and magican of music gear, fixed it for me. It turned out, that effect has two "build in" errors. First was low volume output - maby it was designed for use rather with radio than guitar amp? Who knows. Second was not-very- professional bypas, which results in high noise level, when effect was switch off. Booster is build on Ge(germanium) transistors and built like a tank - about 1,5 mm steel sheet! Works on 9V battery only. Switch is non-profesional too - it's just an ordinary switch, like you can find in lamp.

Credits:
Piotr Salewski