Compatible products: StreetPilot c550, c580, nuvi 650, 660, 670, 680, 750, 760, 770, 780, 755, 765, 775, 785, 850, 880. Traffic tie-ups can't always be prevented. But with Garmin's GTM 20 portable traffic receiver, you can often avoid them. The GTM 20 is an integrated FM TMC (Traffic Message Channel) traffic receiver, antenna and cigarette lighter adapter. Designed exclusively for the American version of compatible Garmin products, it receives digital information (where available) on traffic and road construction tie-ups that your compatible Garmin unit uses to offer an alternate route. TMC data, available in a fast-growing number of cities throughout North America, gives prompt, accurate notification of accidents, road construction, police, or emergency action, etc. -- so you can visually monitor traffic flow and, if necessary, avoid traffic tie-ups. The GTM 20 is a simple plug-and-play solution that combines a self-contained antenna, traffic link and 12-volt cigarette lighter adapter to provide real-time traffic alerts. No professional installation required. Just plug the GTM 20 into your compatible Garmin device, and you're ready to receive data. In most areas, depending on the service provider, TMC traffic broadcasts are continuous -- there's no waiting for scheduled traffic news updates or random alerts. With the GTM 20, you see traffic developments in real-time, as they happen, so you can make the right decision sooner. Because traffic broadcasts are received via a "silent" FM data channel, you can still listen to music or news programming on your car radio without interference from incoming FM traffic data transmissions.