Editing Transmitter (section)

==Regulation==
Two radio transmitters in the same area that attempt to transmit on the same frequency will interfere with each other, causing garbled reception, so neither transmission may be received clearly. [[radio frequency interference|Interference]] with radio transmissions can not only have a large economic cost, it can be life-threatening (for example, in the case of interference with emergency communications or [[air traffic control]]).
 
For this reason, in most countries, use of transmitters is strictly controlled by law.  Transmitters must be licensed by governments, under a variety of license classes depending on use such as [[broadcast]], [[marine radio]], [[Airband]], [[Amateur radio|Amateur]] and are restricted to certain frequencies and power levels. A body called the [[International Telecommunication Union]] (ITU) allocates the [[frequency]] bands in the [[radio spectrum]] to various classes of users. In some classes, each transmitter is given a unique [[call sign]] consisting of a string of letters and numbers which must be used as an identifier in transmissions. The operator of the transmitter usually must hold a government license, such as a [[general radiotelephone operator license]], which is obtained by passing a test demonstrating adequate technical and legal knowledge of safe radio operation.

Exceptions to the above regulations allow the unlicensed use of low-power short-range transmitters in consumer products such as [[cell phone]]s, [[cordless telephone]]s, [[wireless microphone]]s, [[walkie-talkie]]s, [[Wi-Fi]] and [[Bluetooth]] devices, [[garage door opener]]s, and [[baby monitor]]s. In the US, these fall under [[Part 15]] of the [[Federal Communications Commission]] (FCC) regulations. Although they can be operated without a license, these devices still generally must be [[Type approval|type-approved]] before sale.