Beurer PM 58 Operating Instructions Manual page 20

What kind of causes for interference are there?
In some situations, short-range electromagnetic interference can
occur. In order to avoid these, keep well away from these sources.
Nearby power lines
Walking through security gates in airports.
Nearby overhead lines (tram)
Nearby traffic lights, television sets, car motors, bike computers
Nearby exercise equipment
Nearby mobile phones
Interference from other devices for measuring heart rates
The HR monitor as a receiver can react to interfering stray signals
such as other heart rate monitors within a vicinity of one metre. This
can result in incorrect measurements particularly when training in
groups. If you e.g. jog next to one another, it can be beneficial to
wear the HR monitor on the other wrist or to increase the distance to
one's training partner.
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