Thanks dmlavan... I really appreciate the help sir. I could not find this info documented anywhere. Hopefully this post will be searchable for future skippers with similar questions... as I could not find anything like this in my forum searches. So for others future reference:
Dial "A": lets you select which tubes will launch a salvo, i.e. the arrow in the above image is pointing to a salvo of all 4 forward tubes (I, II, III and IV).
Dial "B": sets salvo spread angle
Dial "C": controls running depth
Dial "D": selects an individual torpedo (T) or salvo (S)
Dial "E": selects the torpedo range for those torpedoes that have multiple range/speed settings (L would be long range - slowest speed, S would be short range - fastest speed)
Dial "F": select impact or magnetic fuse - A= contact fuse / M = magnetic