The Comparator Mk II
The Comparator MK III

The object of ranging by sound ranging methods is to bring effective fore to bear on a source of explosive sound in the enemy lines. Normally this source of sounds is a hostile gun troop which it is desired to neutralize immediately, or register for future neutralization , by a heavy concentration of fire.

For ranging purpose it is necessary that the sound ranging organization should have obtained records giving:

 

(a) An approximate location of the area of enemy activity.

(b) A knowledge of our own shells burst fired by a co-operating gun.

 

The comparator allows the differences between the time readings of these two records to be compared by a semi-automatic method, and the errors of the ranging gun in line and range can thuse be deduced.

 

Outline of the method employed

 

If the positions of the tanging gun and the enemy gun are known, its possible to plot the target gun line, and obtain the angles subtended at the enemy gun between the various microphones and GT. The angles are measured in degrees and hafl degrees and are designated right or left according to the position of the particular microphonw in relation to the gun-target line. The apparatus is really a machine for solving a series of particular type of simultaneous equations in two variables.