System - Ball NM2038 Owner's Manual

22. A-PROOF

System

®
MODELS: NM3022
60
D1
60
D2
Direction [D1]: To close the diaphragm
Direction [D2]: To open the diaphragm
42
The patented A-PROOF System in mu-metal is a magnetic trench box
®
located inside the case that protects a mechanical watch against magnetic
fields up to the intensity of 80,000 A/m. Mu-metal is an alloy of nickel,
iron, copper and molybdenum with very high magnetic permeability, which
enables it to deviate static or low-frequency magnetic field lines.
The bottom of the casing includes a retractable diaphragm that allows the
user to look at the movement through the back of the case by maintaining
the diaphragm open when the environment is free of magnetic fields that
could likely damage the movement. The user can then protect this same
movement by closing the diaphragm through a simple rotation of the
bezel. A colored indicator is situated next to the crown to inform the user
if the diaphragm is either open or closed.
• To close the diaphragm, turn the bezel counterclockwise [D1] until the
color of the indicator changes. Make sure not to force the mechanism, it
could get damaged. In the fully closed position, the diaphragm locks the
mu-metal anti-magnetic protection cage and guarantees the antimagnetic
protection described above.
• To open the diaphragm, turn the bezel clockwise [D2] until the color of the
indicator changes. In the retracted position, the diaphragm disappears to reveal
the movement at work through the transparent case-back of the watch.
43