TomTom Runner & Multi-Sport Reference Manual page 13

This symbol shows the strength of GPS reception. While your watch is
looking for GPS satellites, the satellite images flashes.
The heart symbol shows that your watch is connected to a Heart Rate
Monitor. When your watch is trying to connect to the Heart Rate Monitor, the
heart flashes.
The chainring symbol shows that your watch is connected to a Cadence
Sensor. When your watch is trying to connect to the Cadence Sensor, the
chainring flashes.
This symbol shows the battery status.
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