The A158GC is a solid state, plug-in type linear indicating controller designed for precision controlling a slide gate or similar device, either locally or remotely.  It consists primarily of a faceplate with a 0-100% indicating meter, set-point rotary dial, Auto-Off-Manual and Open-Off-Close switches, calibration potentiometers and a printed circuit board. 

The PC board contains the solid state circuitry for amplifying and comparing the feedback signal with the set-point, and output relays for Open/Increase and Close/Decrease.

Indicating lights are provided on the faceplate showing the position of the gate with reference to the set-point.  An internal dead band adjustment (R10) allows compensation for normal inertia or overshoot of the gate drive mechanism.

The A158GC also operates as a constant monitoring device since the indicating meter is on even with the switches in the off (center) position.

The controller circuitry has an internal "fail safe" circuit that automatically closes the gate when the feedback signal is disconnected from the controller for any reason.

COMPONENT DESCRIPTION
1. Auto-Off-Manual Switch: This switch controls the operational mode of the controller. The
    "Auto" position references the Set-point with the feedback signal to switch either relay on.
    The "Manual position bypasses the Set-point and enables the Open-Off-Close Switch.

2. Open-Off-Close Switch:  This switch energizes the corresponding Open/Increase,  
     Closed/Decrease relay in the manual mode, It is a spring loaded return to center (off)
     switch from either direction.

3. Open/Close Lights:   These lights indicate which relay is energized.

4. Set-point:   This is a ten (10) turn "clock" dial potentiometer which provides a precise
     voltage reference for the comparator circuit.  The Set-point is enabled  only in the auto
     position.

5. Zero:  This is a one (1) turn potentiometer  used to electrically "zero" the meter with the gate
     fully closed.

6. Span:  This is a one (1) turn potentiometer used to electrically "span" the meter to 100%
    with the gate fully opened.

7. Meter:   This provides a 0 to100% indication of the gate position.  The meter has a
     mechanical adjustment for "0" indication without power applied.

8. Dead Band:  This is an internal potentiometer (R10) that allows for the electrical adjustment
    of the relays trigger level to match the mechanical overshoot of the gate drive mechanism.
    This adjustment is common to both relay drivers.