It also contains ST radar. I am a little fuzzy on how this works, but it could get a range to the target. Both have horizontal lines in them where if you have an estimate of the target masthead height, you can count the number of horizontal lines it crosses and get a rough idea of the target range. It has automatic input of the submarine course and speed. It also has a section for the target.
Basic object is to expeditiously determine the relative movement of the target.
This phase commences with the first indication of an enemy target in the vicinity, either by radar, visual, or sound. The duration of this phase is the period from the initial contact until the approach phase commences. The object of this phase is to aggressively and tenaciously close the enemy to a favorable position for the attack. During this phase there is opportunity to determine the type of target. Flags flying, Guns, Radars, Riding high or low, Deck cargo, People on deck, any special rig, Light burning, Length, Mast height.