Aktungbby has a quote there: "
THIS ALLOWED FOR CONSTANT POSITION UPGRADES The position keeper solves the equations of motion integrated over time. The result is a continuous prediction of where the target is at any instant. Successive measurements of the targets' position are compared to the position keeper predictions and corrections for error are introduced with the hand cranks. The predicted target position becomes more accurate as more measurements make the corrections smaller. It is typical to get an accurate track on the target after about three or four observations under good conditions."
... and the diagram shows the inputs on the left and near the top for several "real-time" data updates that flow through the "Receiver" section, with multiple choices for data flow and inputs, whether periscope, hydrophone, whatever, along with updates of the subs own course and speed - looks to me, anyway. It also looks like any "adjustments" made with the hand cranks at the receiver fed back to the "measuring device" stations. The Mark 18 is a copy of a German electric torpedo found onshore US in 1942 (although the US had been working on one already, and the Mark 4 came out in 1943... one of my "searches" brought up a revovly link, which is nothing more than the wikipedia.org article on the mark 18, and it showed "The Mark 4 was developed to support the Mark 18 torpedo...", but I could not find that in the text itself (old eyes??)...
If you're anywhere near Washington state (Keyport), it might worth the while to visit
http://www.navalunderseamuseum.org/permanent/
They say they have a Mark 4 there in the Silent Victory exhibit.