Travel-scale.—A scale for making corrections for angular travel of the target; there are two, one below the azimuth correction-scale and one on the platen.
"T" Square.—The sliding "T" square having the time graduations at one edge, corresponding to given ranges.
OPERATION.
Place the travel-scale on the platen in the lower or upper position according as the observing interval is 10 or 20 seconds.
As soon as the wind-component device is set note the deflection reference-number indicated, and set the wind-arm to the corresponding reading on the wind-component scale.
Set the platen so that the point of the drift-curve corresponding to the given range will be accurately over the right-hand edge of the wind-arm.
As soon as the reference-number indicating the angular travel of the target during the observing interval is announced, set the travel-arm (right edge) for that travel by the travel-scale on the platen and set the azimuth correction-scale for the same travel by means of the travel-scale below it.
Set the "T" square so that the point of its scale corresponding to the given range will be accurately over the right edge of the travel-arm.
The azimuth correction to be applied to the gun-arm in all cases is then read from the azimuth correction scale at the bevel edge of the "T" square.
When Case I or II is being used the deflection to be sent to the guns is read from the deflection-scale at the bevel edge of the "T" square.