Hi
From memory;
There are Hall sensors within the handlebar ( that are not readily visible ).
There is a pair of magnets ( small short rod/cylinder style ) in/on the twist grip.
Thus there's a weatherproof link.
Error conditions include:
1 A magnet is missing.
2 A magnet is installed in the wrong orientation.
3 Both magnets are installed in the wrong orientation.
Michael
www.dgbint.com