[[File:Joint Tactical Information Distribution System Users, 1990.jpg|thumb|320px|Joint Tactical Information Distribution System Users, 1990]]
The '''Joint Tactical Information Distribution System (JTIDS)''' is/was an [[L band#IEEE L band|L band]] Distributed Time Division Multiple Access (DTDMA) network radio system used by the [[United States armed forces]] and their allies to support [[data communication]]s needs, principally in the air and missile defense community. It produces a [[spread spectrum]] signal using frequency [[Frequency-shift keying]] (FSK) and [[Phase-shift Shift Keyingkeying]] (PSK) to spread the radiated power over a wider spectrum (range of frequencies) than normal radio transmissions. This reduces susceptibility to noise, jamming, and interception. In Time Division Multiple Access (TDMA) (supposedly like cell phone systems), each time interval (e.g. 1 second) is divided into time slots (e.g. 1024 per second). Together, all the time slots in the interval are called a "frame". Each slot is "bursted" (transmitted) at a different frequency (FSK). Within each slot, the phase angle of the transmission burst can be varied to provide PSK. Each type of data to be transmitted is assigned a slot or block of slots (channel). In TDMA, the slot frequencies remain fixed from second to second (frame to frame). In DTDMA, the slot frequencies and/or slot assignments for each channel do not remain fixed from frame to frame but are varied in a pseudo-random manner. The slot assignments, frequencies, and information may all be encrypted to provide computer-to-computer connectivity in support of every type of military platform from [[U.S. Air Force|Air Force]] [[Fighter aircraft|fighters]] to [[United States Navy|Navy]] [[submarine]]s.
The full development of JTIDS commenced in 1981 when a contract was placed with Singer-Kearfott (later GEC-Marconi Electronic Systems, now [[BAE Systems Electronics and Integrated Solutions|BAE Systems E&IS]]). Fielding proceeded slowly throughout the late 1980s and early 1990s with rapid expansion (following [[9-11|9/11]]) in preparation for Operation Enduring Freedom (Afghanistan) and Operation Iraqi Freedom. Development is now carried out by [[Data Link Solutions LLC|Data Link Solutions]], a joint BAE/[[Rockwell Collins]] company.
