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 certain 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 and Europe, 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. Receive Real-time Traffic Data In most areas, depending on the service provider, TMC traffic broadcasts are continuous — theres 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. The system alerts you when a traffic problem is on your route and proposes an alternate route to avoid the incident. 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. The GTM 20 is a portable, all-in-one antenna, traffic receiver, and 12-volt cigarette adapter that does not require professional installation.