Range 50/100 meters range to port and starboard. Scale lines (one pixel wide, inverse video) divide the image width into 10 mtr. Equal increments when set to 50 meters. When set to 100 meters increments equal 20 meters.

Towfish Height control enables removal of the water column from the printout. With this control set to 0 meters, there will generally be two echoes either side of the towfish track down the center of the printout. The strong signal will be from the sea bed and the weak signal will be from the surface.

The scale lines allow good estimates to be made of the towfish height from the sea bed and it's depth below the surface. As the towfish is lowered towards the sea bed, the surface signal will get weaker and also farther from the center of the printout whilst the bed signal will get closer to the center.

When the towfish is flying at the correct altitude, the wasted center section of the printout may be utilized by setting the Towfish Height control to equal the estimated height of the towfish from the sea bed. However, in so doing, you lose your check on the safe height of the towfish

(0 to 15 meters water column removal potentiometer).

Towfish speed control adjusts the print speed in order to correct for various speeds over ground (which may not be the same as the speed through the water, depending on tidal currents). 1 to 5 knots speed over ground correction potentiometer.

Print Test momentary pushbutton to advance a 16 level gray scale pattern.

Advance Paper momentary pushbutton to advance white paper.

Threshold potentiometer to set first gray level on the test pattern to just visible.

Contrast potentiometer to set darkest gray level on the test pattern to full black.