W&H Perfecta 900 Instructions For Use Manual page 33

Change the rotary tool
When the chuck is open, the motor handpiece is blocked . In the event that the motor handpiece starts accidentally, the
electronic system switches off .
Test run
> Start the motor handpiece .
> In the event of malfunctions (e .g . vibrations, unusual noises, overheating), stop the motor immediately und contact an
authorized W&H service partner (see page 45) .
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