Perhaps my poor choice of words, as I don't know actually how simple it is to input the data. I was also going by the schematic near the bottom here (this is for a Mk.IV -
http://www.usscod.org/tdc-restore.html ). Sz is torpedor running speed. Another source I have somewhere mentioned that the TDC operator had to "input torpedo type and speed", but obviously if torp. speed is a discrete input parameter, then type would surely be unnecessary?