Bought this specifically for a trip to Belgium, it really is plug and play. My Garmin 550 detected the signals straight away and helped us avoid sitting at the back of a long queue. On the one occasion I ignored it we had to drive very slowly on to the M25, so lesson learnt.
The 550 shows when it has a signal and there are no delays, or the number of minutes and location of the blockage, e.g. Derby 2 minutes.
Even in Europe all worked great and eased the stress of driving and navigation in an unfamiliar situation.
Only two negatives which prevent 5 stars - the price, and the fact that I think this sort of equipment should be included with the original purchase.