Audiovox SMT 5600 / SPV C500 (HTC Typhoon)

The classes mainly refer to the wireless range that the devices can be apart. Class one for instance allows you to connect hardware up to 100 meters (330 feet) away. Class 2 runs about 10 meters (30 feet). Class 1 devices however are backward compatible with class 2 devices. You'll see class 2 devices around more than you will class 1 for reasons someone else can explain (my guess is that it was more widely adopted as the standard--kinda like how 802.11a went). Hope this helps!