Some ships carry degaussing equipment to reduce the signal detected by a magnetic pistol.
During World War II, Japan employed a mechanical remote detonator in order to replicate the functionality of magnetic proximity fuzes used by torpedoes of other navies, such as Germany and the United States.
Using a mechanical device circumvented the problems inherent with magnetometric influence sensing.
This device, called the Type 1 Detonator T-Device (一式起爆装置T装置, Isshiki Kibaku Sōchi T-Sōchi), featured a tethered underwater kite (凧) which deployed from the head of the torpedo after launch, unreeling the tether under gradual tension.
The kite would physically collide with the hull of a target surface vessel, whereupon it would sever the tether.