In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication channel or storage in a storage medium. An early example is an invention of language, which enabled a person, through speech, to communicate what they thought, saw, heard, or felt to others. But speech limits the range of communication to the distance a voice can carry and limits the audience to those present when the speech is uttered. The invention of writing, which converted spoken language into visual symbols, extended the range of communication across space and time.
Signals intelligence (SIGINT) is the act and field of intelligence-gathering by interception of signals, whether communications between people or from electronic signals not directly used in communication. As classified and sensitive information is usually encrypted, signals intelligence may necessarily involve cryptanalysis. Traffic analysis—the study of who is signaling to whom and in what quantity—is also used to integrate information, and it may complement cryptanalysis.
Wireless telegraphy or radiotelegraphy is the transmission of text messages by radio waves, analogous to electrical telegraphy using cables. Before about 1910, the term wireless telegraphy was also used for other experimental technologies for transmitting telegraph signals without wires. In radiotelegraphy, information is transmitted by pulses of radio waves of two different lengths called "dots" and "dashes", which spell out text messages, usually in Morse code. In a manual system, the sending operator taps on a switch called a telegraph key which turns the transmitter on and off, producing the pulses of radio waves. At the receiver the pulses are audible in the receiver's speaker as beeps, which are translated back to text by an operator who knows Morse code.
Automatic Link Establishment, commonly known as ALE, is the worldwide de facto standard for digitally initiating and sustaining HF radio communications. ALE is a feature in an HF communications radio transceiver system that enables the radio station to make contact, or initiate a circuit, between itself and another HF radio station or network of stations. The purpose is to provide a reliable rapid method of calling and connecting during constantly changing HF ionospheric propagation, reception interference, and shared spectrum use of busy or congested HF channels.
A message is a unit of communication that conveys information from a sender to a receiver. It can be transmitted through various forms, such as spoken or written words, signals, or electronic data, and can range from simple instructions to complex information.
Tactical communications are military communications in which information of any kind, especially orders and military intelligence, are conveyed from one command, person, or place to another upon a battlefield, particularly during the conduct of combat. It includes any kind of delivery of information, whether verbal, written, visual or auditory, and can be sent in a variety of ways. In modern times, this is usually done by electronic means. Tactical communications do not include communications provided to tactical forces by the Defense Communications System to non-tactical military commands, to tactical forces by civil organizations, nor does it include strategic communication.
Optical communication, also known as optical telecommunication, is communication at a distance using light to carry information. It can be performed visually or by using electronic devices. The earliest basic forms of optical communication date back several millennia, while the earliest electrical device created to do so was the photophone, invented in 1880.
The National Security Agency took over responsibility for all US government encryption systems when it was formed in 1952. The technical details of most NSA-approved systems are still classified, but much more about its early systems have become known and its most modern systems share at least some features with commercial products.
Flag signals can mean any of various methods of using flags or pennants to send signals. Flags may have individual significance as signals, or two or more flags may be manipulated so that their relative positions convey symbols. Flag signals allowed communication at a distance before the invention of radio and are still used especially in connection with ships.
A secret broadcast is, simply put, a broadcast that is not for the consumption of the general public. The invention of the wireless was initially greeted as a boon by armies and navies. Units could now be coordinated by nearly instant communications. An adversary could glean valuable and sometimes decisive intelligence from intercepted radio signals:
A signaller, signalman, colloquially referred to as a radioman or signaleer in the armed forces is a specialist soldier, sailor or airman responsible for military communications. Signallers, a.k.a. Combat Signallers or signalmen or women, are commonly employed as radio or telephone operators, relaying messages for field commanders at the front line, through a chain of command which includes field headquarters. Messages are transmitted and received via a communications infrastructure comprising fixed and mobile installations.
The United States Army Signal Corps (USASC) is a branch of the United States Army that creates and manages communications and information systems for the command and control of combined arms forces. It was established in 1860, the brainchild of Major Albert J. Myer, and had an important role in the American Civil War. Over its history, it had the initial responsibility for portfolios and new technologies that were eventually transferred to other U.S. government entities. Such responsibilities included military intelligence, weather forecasting, and aviation.
The Royal Australian Corps of Signals (RASigs) is one of the 'arms' of the Australian Army. It is responsible for installing, maintaining, and operating all types of telecommunications equipment and information systems. The motto of the Signals Corps is Certa Cito and is translated as 'Swift and Sure', signifying the aim of the signal service – that communication be carried out with maximum speed and certainty. Like their British counterparts, the Royal Australian Corps of Signals' flag and hat badge feature Mercury, the winged messenger of the gods, affectionately referred to by members of the corps as "Jimmy".
A communications officer is a naval line officer responsible for supervising operation and maintenance of a warship's signal flags, signal lamps, and radio transmitters and receivers. The communications officer is usually responsible for encrypting and decrypting secret message traffic and for distribution and safe storage of secret messages. Aboard some ships, the communications officer is responsible for the ship's secret publications inventory or for the ship's post office and distribution of mail.
The Royal Signals trades are the employment specialisations of the Royal Corps of Signals in the British Army. Every soldier in the Corps is trained both as a field soldier and a tradesman. There are currently six different trades, all of which is open to both men and women:
The British Armed Forces operates a wide range of communications and information systems (CIS). Some of these are specialised military systems, while others are procured off-the-shelf. They fall into three main categories: satellite ground terminals, terrestrial trunk communications systems, and combat net radio systems. Every part of the British Army uses combat net radio, but only the Royal Corps of Signals and the Royal Air Force operates trunk systems and multi-channel satellite communications.
Indian Army Corps of Signals is a corps and a combat support arm of the Indian Army, which handles its military communications. It was formed on 15 February 1911 as a separate entity under Lieutenant Colonel S H Powell, and went on to make important contributions to World War I and World War II. The corps celebrated its 100-year anniversary of its raising on 15 February 2010.
Semaphore is the use of an apparatus to create a visual signal transmitted over distance. A semaphore can be performed with devices including: fire, lights, flags, sunlight, and moving arms. Semaphores can be used for telegraphy when arranged in visually connected networks, or for traffic signalling such as in railway systems, or traffic lights in cities.
The Russian Signal Troops , also known as the Signal Communications Troops, is a Combat Arm of the Russian Ground Forces, responsible for military communications.
Wigwag is an historical form of flag signaling that passes messages by waving a single flag. It differs from flag semaphore in that it uses one flag rather than two, and the symbols for each letter are represented by the motion of the flag rather than its position. The larger flag and its motion allow messages to be read over greater distances than semaphore. Messages could be sent at night using torches instead of flags.
