Abstract: A motion monitor apparatus includes a monitoring housing with a projecting encoder shaft having an encoding disc on the inner end. The outer peripheral portion of the disc is imprinted with equicircumferentially distributed opaque sections. A pair of photo detectors are mounted with U-shaped arms having a light emitting diode to one side of the disc and a phototransistor to the opposite side. A signal processing circuit within the housing includes a pair of channels. Each channel includes a dual input gate connected to a resettable monostable multivibrator having a pulse width resistor-capacitor network have a variable resistor to adjust the output pulse width. The monostables have inhibit inputs and the outputs interconnected for various response conditions including dual directional response, single direction response or indicated opposite direction response. The processed pulse signals are impressed on an integrating capacitor which is coupled to drive a transistor.