at the input (Grid of V-3A) of the first Schmitt Trigger. Then adjust R-23 until the Schmitt circuit just triggers. 5e Second Schmitt Trigger (V-6) - With five pulses per train from the information unit, adjust R-33 so that the second Sohmitt triggers on the fifth pulse from the first Schmitt. 6. Third Schmitt trigger (V-10) sensitivity - R-li8 gives a range of control from a point where the Schmitt cannot be fired to where the Schmitt fires more than once per period. R-i8 should be adjusted to a point midway between these extremes to insure reliable operation of the grounding relay, K-1. elbe2 Calibration Procedure 1. Press the release button and sero the recorder with the sere "SET" control. 2e Set the arm of R-76 to zero volts. (This control is mounted on the rear of the chassis). Je Feed a signal of 90 pulses per train (from the information station) to the input of the Receiving Station, and bring the recorder to full soale by adjusting R-44, he Reduce the number of pulses per train to five, and adjust R-76 until the recorder reads sero. This adjustment bucks out the potential developed across the integrating capacitors by the initial five pulses. 5. Several check points over the full range should be taken by introducing appropriate signals from the information unit.