[TorpX]

Originally Posted by ColonelSandersLite

Given that there is no way to input submarine speed or stabilization distance, and the computer that could do it probably couldn't fit into the periscope...

This had to be done by the TDC. As you say, the machinery couldn't fit in the scope. But why would it need to? The outputs from the TDC could be fed into the mechanism to move the line. The position keeper already calculates and updates the target position, so not much else is required.

I think it's safe to assume that the line was stabilized to infinity. This means that there is just no practical difference between just using a regular vertical line on the periscope and using the stabilized line so long as the submarine is not turning.

I think this is a further indication that the TDC did indeed calculate the info for the line to move. Otherwise, the whole point is lost.