Sigma ONYX EASY Mode D'emploi page 60

Important If no heart rate is shown on the display, this may
be due to the following reasons:
note
k The belt with the heart rate transmitter is not
worn correctly
k The sensors (electrodes) on the heart rate
transmitter are dirty or dry
k Interference from electrical sources (high voltage
lines, railway cables, etc.)
k Transmitter battery (CR 2032) is dead
(Item no. 00342)
PAGE 28
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Before starting to train, consult your doctor
to avoid risks to your health. This applies in
particular if you have cardio-vascular
problems.
7.5 Changing the
battery/waterproofing
and warranty
Special key for opening the battery
compartment.