“The DOD FX35 Octoplus debuted in mid-1986. Its original circuit appears to be at least loosely based on the original Boss OC-2 Octaver schematic, with a flip-flop IC as an octave divider and four op amps in addition to the components used for the clickless FET foot switch. Unlike the Boss OC-2, the FX35 features a tone control (boosts bass or treble of the octave signal only), and only one sub-octave note is created. Like all octave dividers, the FX35 cannot track chords very well (although root-fifth power chords can sound okay, at least until one note starts to warble out), but tracking can be enhanced by using your neck pickup and/or adding a boost or compression pedal before the FX35. The FX35 was discontinued by late 1994.”
More information here:
