Default setting for Torpedo pistol selector?

[Mittelwaechter]

The pistol was a combination of an 'allways on' impact mechanism plus a magnetically triggered electric mechanism - switchable to be on/off.
Why should there have been a problem to switch this electric function on/off at torpedos in the tubes, while they could be simply manipulated for running depth, speed and gyroangle?
To switch the mag fuse off you would have had to disconnect/switch an electric circuit and the system would have been disabled.

They had to care for the sensitivity of the magnetic mechanism due to different intensities of the earth magnetic field in different regions.
Therefore they had to remove the torpedos from the tubes to update the mag fuse settings for the current region - as for several other maintenance.
It was a huge problem in the North Sea, because there are pretty much iron ore fields in rather shallow water conditions to irritate the mag fuse.
It was one of the reasons for premature detonations or duds under the keel - they simply didn't match the required sensitivity conditions.

The other major problem with the German torpeos was a little calibrated pressure chamber inside the torpedos - relevant for keeping the set running depth.
This chamber was leaky and influenced by the high pressure conditions during deep diving periods of the U-Boot.