Moog modular synthesizer

The first prototype Moog Modular Synthesizer, designed by Bob Moog was built in 1964 and by 1967 was a commercially available product line. These consisted of Moog 900-series modules housed in walnut cabinets. The 900-series modules use S-Trigger, which drops a +5V level to 0V when a trigger is sent, and not the more widely used Gate which raise 0V to a higher voltage.