Conveyor system control circuit

In a system wherein a traveling carrier mechanism is moved in a track and selectively controlled in its movement including an encoder unit mounted on the mechanism and a readout unit mounted along the path and wherein the encoder unit provides a code comprising a pluraity of input signals and the readout unit along the track reads the signals to actuate a track switch and determine the path of movement of the traveling carrier mechanism, the improvement comprising

• a control circuit associated with said encoder unit and comprising a readout circuit and a logic circuit,
• said readout circuit including an AND circuit having an input for receiving signals from the encoder unit and transmitting an output signal when the code on the encoder unit matches the code on the readout unit,
• said logic circuit having an input and an output,
• means for coupling the output of said readout circuit and the input of the logic circuit while maintaining the readout circuit electrically isolated from the logic circuit,
• and means for coupling the output of the logic circuit and the track switch along the path of the traveling carrier mechanism while maintaining the logic circuit and the track switch electrically isolated from one another,
• said readout circuit comprising a plurality of input buffers for sensing the presence or absence of an externally originating signal from said encoder unit and for sensing the presence or absence of simultaneous code signals from the encoder unit.