In Bluetooth, "class" refers to the three levels of power for Bluetooth devices: Class 1, 2, and 3. The following table compares power and range of these three classes:
|BT Class||>Maximum Power||Operating Range|
|Class 1||100 mW (20 dBm)||100 meters|
|Class 2||2.5 mW (4 dBm)||10 meters|
|Class 3||1 mW (0 dBm)||1 meter|
To communicate over the 100 meter range, a class 1 BT device is required at both ends. To communicate over the 10 meter range, a class 1 or class 2 device is required at both ends.
Note: Class 3 devices are uncommon due to their very limited range.