This is Ibanez' first guitar effect pedal which was sold officially and internationally. The Phase Tone is a MXR Phase 90 knock-off and like the MXR the PT-900 has a slightly distorted sound with humbucking pickups. The second issue (inscription "Phase Tone" below Ibanez) sports a modified circuit with less distortion. The PT-900 was available through different brand names like Greco, Pax and Foot System.
Speed knob controls the speed/rate of the LFO wave that shapes the effect.
