Radio silence
Encyclopedia
In telecommunications, radio silence is a status in which all fixed or mobile radio station
s 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.
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.
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:
, or in nautical and aeronautical communications to allow faint distress calls to be heard (see Mayday
). In the latter case, the controlling station can order other stations to stop transmitting with the proword "Seelonce Seelonce Seelonce". (The word uses the French pronunciation of the word silence, "See-LAWNCE."). Once the need for radio silence is finished, the controlling station lifts radio silence by the prowords "Seelonce FINI."
Disobeying a Seelonce Mayday order constitutes a serious criminal offence in most countries.
The aviation equivalent of Seelonce Mayday is the phrase or command "Stop Transmitting - Distress (or Mayday)". "Distress traffic ended" is the phrase used when the emergency is over. Again, disobeying such an order is extremely dangerous and is therefore a criminal offence in most countries.
In the USA
, CONELRAD
, EBS
and EAS
were also a way of maintaining radio silence, mainly in broadcasting
, in the event of an attack.
Radio station
Radio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
s 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.
Military
An order for Radio silence is generally issued by the militaryMilitary
A military is an organization authorized by its greater society to use lethal force, usually including use of weapons, in defending its country by combating actual or perceived threats. The military may have additional functions of use to its greater society, such as advancing a political agenda e.g...
where any radio transmission may reveal troop
Troop
A troop is a military unit, originally a small force of cavalry, subordinate to a squadron and headed by the troop leader. In many armies a troop is the equivalent unit to the infantry section or platoon...
positions, either audibly from the sound of talking, or by radio direction finding
Radio direction finder
A radio direction finder is a device for finding the direction to a radio source. Due to low frequency propagation characteristic to travel very long distances and "over the horizon", it makes a particularly good navigation system for ships, small boats, and aircraft that might be some distance...
. In extreme scenarios Electronic Silence ('Emissions Control' or EMCON
EMCON
EMCON is a military condition in which electromagnetic emissions do not exceed a set limit. This helps to avoid electronic detection. The EMCON condition can be passed via an EMCON bill, directives, OP orders, message traffic or embarked or area commander.-External links:* ....
) may also be put into place as a defence against interception.
In the British Army
British Army
The British Army is the land warfare branch of Her Majesty's Armed Forces in the United Kingdom. It came into being with the unification of the Kingdom of England and Scotland into the Kingdom of Great Britain in 1707. The new British Army incorporated Regiments that had already existed in England...
, the imposition and lifting of radio silence will be given in orders or ordered by control using 'Battle Code' (BATCO
BATCO
BATCO, short for Battle Code, is a hand-held, paper-based encryption system used at a low, front line level in the British Army during the late Cold War period....
). 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
BATCO
BATCO, short for Battle Code, is a hand-held, paper-based encryption system used at a low, front line level in the British Army during the late Cold War period....
to break radio silence.
The command for imposing radio silence is:
-
- "Hello all stations, this is 0. Impose radio silence. Over."
Non-military radio silence orders
Radio silence can also be maintained for other purposes, such as for highly sensitive radio astronomyRadio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
, or in nautical and aeronautical communications to allow faint distress calls to be heard (see Mayday
Mayday (distress signal)
Mayday is an emergency procedure word used internationally as a distress signal in voice procedure radio communications. It derives from the French venez m'aider, meaning "come help me"....
). In the latter case, the controlling station can order other stations to stop transmitting with the proword "Seelonce Seelonce Seelonce". (The word uses the French pronunciation of the word silence, "See-LAWNCE."). Once the need for radio silence is finished, the controlling station lifts radio silence by the prowords "Seelonce FINI."
Disobeying a Seelonce Mayday order constitutes a serious criminal offence in most countries.
The aviation equivalent of Seelonce Mayday is the phrase or command "Stop Transmitting - Distress (or Mayday)". "Distress traffic ended" is the phrase used when the emergency is over. Again, disobeying such an order is extremely dangerous and is therefore a criminal offence in most countries.
In the USA
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, CONELRAD
CONELRAD
CONELRAD was a method of emergency broadcasting to the public of the United States in the event of enemy attack during the Cold War. It was intended to serve two purposes; to prevent Soviet bombers from homing in on American cities by using radio or TV stations as beacons, and to provide...
, EBS
Emergency Broadcast System
The Emergency Broadcast System was an emergency warning system in the United States, used from 1963 to 1997, when it was replaced by the Emergency Alert System.-Purpose:...
and EAS
Emergency Alert System
The Emergency Alert System is a national warning system in the United States put into place on January 1, 1997, when it superseded the Emergency Broadcast System , which itself had superseded the CONELRAD System...
were also a way of maintaining radio silence, mainly in broadcasting
Broadcasting
Broadcasting is the distribution of audio and video content to a dispersed audience via any audio visual medium. Receiving parties may include the general public or a relatively large subset of thereof...
, in the event of an attack.
Radio silence orders
- Radio silencing occurred after Japan attacked Pearl HarborAttack on Pearl HarborThe attack on Pearl Harbor was a surprise military strike conducted by the Imperial Japanese Navy against the United States naval base at Pearl Harbor, Hawaii, on the morning of December 7, 1941...
in World War IIWorld War IIWorld War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
using AM radio station KGU in Honolulu as a homing signal. - On June 2, 1942, during WWII, a nine-minute air-raid alert, including at 9:22 pm a radio silence order applied to all radio stationRadio stationRadio broadcasting is a one-way wireless transmission over radio waves intended to reach a wide audience. Stations can be linked in radio networks to broadcast a common radio format, either in broadcast syndication or simulcast or both...
s from MexicoMexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
to CanadaCanadaCanada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
See also
- Guard bandGuard band-Radio and electronic signalling:In radio, a guard band is an unused part of the radio spectrum between radio bands, for the purpose of preventing interference....
- EMCONEMCONEMCON is a military condition in which electromagnetic emissions do not exceed a set limit. This helps to avoid electronic detection. The EMCON condition can be passed via an EMCON bill, directives, OP orders, message traffic or embarked or area commander.-External links:* ....
- The Zone of Silence
- United States National Radio Quiet ZoneUnited States National Radio Quiet ZoneThe United States National Radio Quiet Zone is a large area of land surrounding the National Radio Astronomy Observatory at Green Bank, West Virginia, and especially the large Green Bank Telescope radio telescope. The Radio Quiet Zone is a rectangle of land approximately in size that straddles...