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In telecommunications, radio silence or Emissions Control (EMCON) is a status in which all fixed or mobile radio stations in an area are asked to stop transmitting for safety or security reasons. The term "radio station" may include anything capable of transmitting a radio signal. A single ship, aircraft, spacecraft, or group of them may also maintain radio silence.〔(Iraqi ships maintaining radio silence ) The Guardian〕 == Military == An order for ''Radio silence'' is generally issued by the military where any radio transmission may reveal troop positions, either audibly from the sound of talking, or by radio direction finding. In extreme scenarios Electronic Silence ('Emissions Control' or EMCON) may also be put into place as a defence against interception. 〔(Emissions Control 3 Mission ) Airforce Technology 〕 In the British Army, the imposition and lifting of radio silence will be given in orders or ordered by control using 'Battle Code' (BATCO). Control is the only authority to impose or lift radio silence either fully or selectively. The lifting of radio silence can only be ordered on the authority of the HQ that imposed it in the first place. During periods of radio silence a station may, with justifiable cause, transmit a message. This is known as Breaking Radio Silence. The necessary replies are permitted but radio silence is automatically re-imposed afterwards. The breaking station transmits its message using BATCO to break radio silence. The command for imposing radio silence is: Hello all stations, this is 0. Impose radio silence. Over. Other countermeasures are also applied to protect secrets against enemy signals intelligence. Electronic emissions can be used to plot a line of bearing to an intercepted signal, and if more than one receiver detects it, triangulation can estimate its location. Radio Detection Finding (RDF) was critically important during the Battle of Britain and reached a high state of maturity in early 1943 with the aid of United States institutions aiding British Research and Development under the pressures of the continuing Battle of the Atlantic during World War II when locating U-boats. One key breakthrough was marrying MIT/Raytheon developed CRT technology with pairs of RDF antennas giving a differentially derived instant bearing useful in tactical situations, enabling escorts to run down the bearing to an intercept. The U-boat command of Wolfpacks required a minimum once daily communications check-in, allowing new Hunter-Killer groups to localize U-boats tactically from April on, leading to the dramatic swing the fortunes of war in the battle between March, when the U-boats sank over 300 allied ships and "Black May" when the allies killed at least 44 U-boats—each with orders to not exercise EMCON/radio silence. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Radio silence」の詳細全文を読む スポンサード リンク
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