The rules for transmitters operating in the 902-928MHz and 2400-2483.5MHz bands are governed by Part 15.247 for spread spectrum radios and by 15.249 for narrow band radios. The rules only specify output power, harmonic levels, and bandwidth as well as the details of the spread spectrum techniques. There are no restrictions on the type of application, how long the radios can transmit, or how often they can transmit. This has made these bands very popular for general use data, video, and audio applications. The 2.4GHz band is extremely popular because it is allowed in just about every country in the world. This enables manufacturers to make one product and sell it globally. It also means that there is a lot of competition and potential interference. Typical applications in the 900MHz band include data modems, sensor networks, active RFID, intercom and audio links, and some video links. Typical applications in the 2.4GHz band include data modems, WiFi, Bluetooth, sensor networks, audio and video links.