The Defense Information Systems Agency (DISA), known as the Defense Communications Agency (DCA) until 1991, is a United States Department of Defense (DoD) combat support agency composed of military, federal civilians, and contractors. DISA provides information technology (IT) and communications support to the President, Vice President, Secretary of Defense, the military services, the combatant commands, and any individual or system contributing to the defense of the United States.
Very high frequency (VHF) is the ITU designation for the range of radio frequency electromagnetic waves from 30 to 300 megahertz (MHz), with corresponding wavelengths of ten meters to one meter. Frequencies immediately below VHF are denoted high frequency (HF), and the next higher frequencies are known as ultra high frequency (UHF).
Single Channel Ground and Airborne Radio System (SINCGARS) is a very high frequency combat network radio (CNR) used by U.S. and allied military forces. In the CNR network, the SINCGARS’ primary role is voice transmission between surface and airborne command and control (C2) assets.
4DTV is a proprietary broadcasting standard and technology for digital cable broadcasting and C-band/Ku-band satellite dishes from Motorola, using General Instrument's DigiCipher II for encryption. It can tune in both analog VideoCipher II and digital DCII satellite channels.
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for amateur radio communications, international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
Satellite Internet access is Internet access provided through communication satellites; if it can sustain high speeds, it is termed satellite broadband. Modern consumer grade satellite Internet service is typically provided to individual users through geostationary satellites that can offer relatively high data speeds, with newer satellites using the Ku band to achieve downstream data speeds up to 506 Mbit/s. In addition, new satellite internet constellations are being developed in low-earth orbit to enable low-latency internet access from space.
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.
End-to-end encryption (E2EE) is a private communication system in which only communicating users can participate. As such, no one else, including the communication system provider, telecom providers, Internet providers or malicious actors, can access the cryptographic keys needed to converse. End-to-end encryption is intended to prevent data being read or secretly modified, other than by the true sender and recipient(s). The messages are encrypted by the sender but the third party does not have a means to decrypt them, and stores them encrypted. The recipients retrieve the encrypted data and decrypt it themselves. Because no third parties can decipher the data being communicated or stored, for example, companies that provide end-to-end encryption are unable to hand over texts of their customers' messages to the authorities.
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.
Television encryption, often referred to as scrambling, is encryption used to control access to pay television services, usually cable, satellite, or Internet Protocol television (IPTV) services.
A motorcade, or autocade, is a procession of motor vehicles. Uses can include ceremonial processions for funerals or demonstrations, but can also be used to provide security while transporting a very important person. The American presidential motorcade is an example of both and is a staple of public appearances by the president of the United States.
In aviation, ACARS is a digital datalink system for transmission of short messages between aircraft and ground stations via airband radio or satellite. The protocol was designed by ARINC and deployed in 1978, using the Telex format. More ACARS radio stations were added subsequently by SITA.
Bowman is the name of the tactical communications system used by the British Armed Forces.
Mobile radio or mobiles refer to wireless communications systems and devices which are based on radio frequencies, and where the path of communications is movable on either end. There are a variety of views about what constitutes mobile equipment. For US licensing purposes, mobiles may include hand-carried,, equipment. An obsolete term is radiophone.
The AN/PRC-148 Multiband Inter/Intra Team Radio (MBITR) is the most widely fielded handheld multiband, tactical software-defined radio, used by NATO forces around the world. The radio is built by Thales Communications, a subsidiary of the France-based Thales Group. The designation AN/PRC translates to Army/Navy Portable Radio used for two-way communications, according to Joint Electronics Type Designation System (JETDS) guidelines.
Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave. They can be received by other antennas connected to a radio receiver, this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.
FASCINATOR is a series of Type 1 encryption modules designed in the late-1980s to be installed in Motorola SECURENET-capable voice radios. These radios were originally built to accept a DES-based encryption module that was not approved by NSA for classified communications. The FASCINATOR modules replaced the DES units and can be used for classified conversations at all levels when used with appropriately classified keys. FASCINATOR operates at 12 kbit/s for encryption and decryption. It is not compatible with DES-based voice systems.
NXDN stands for Next Generation Digital Narrowband, and is an open standard for public land mobile radio systems; that is, systems of two-way radios (transceivers) for bidirectional person-to-person voice communication. It was developed jointly by Icom Incorporated and Kenwood Corporation as an advanced digital system using FSK modulation that supports encrypted transmission and data as well as voice transmission. Like other land mobile systems, NXDN systems use the VHF and UHF frequency bands. It is also used as a niche mode in amateur radio.
Digital mobile radio (DMR) is a digital radio standard for voice and data transmission in non-public radio networks. It was created by the European Telecommunications Standards Institute (ETSI), and is designed to be low-cost and easy to use. DMR, along with P25 phase II and NXDN are the main competitor technologies in achieving 6.25 kHz equivalent bandwidth using the proprietary AMBE+2 vocoder. DMR and P25 II both use two-slot TDMA in a 12.5 kHz channel, while NXDN uses discrete 6.25 kHz channels using frequency division and TETRA uses a four-slot TDMA in a 25 kHz channel.
A ground segment consists of all the ground-based elements of a space system used by operators and support personnel, as opposed to the space segment and user segment. The ground segment enables management of a spacecraft, and distribution of payload data and telemetry among interested parties on the ground. The primary elements of a ground segment are:
