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Commutation (telemetry)
In telemetry, commutation is a process whereby multiple data streams ("measurands"), possibly with differing data rates, are combined into a single Frame (networking), frame-based stream for transmission (telecommunications), transmission, before being separated again (decommutated) upon reception; it is a form of time-division multiplexing. Frame synchronization must be achieved before a data stream can be decommutated. Etymology Commutation is named by analogy with Commutator (electric), electric commutators, which engage multiple electrical contacts in sequence as they rotate; similarly, telemetry commutation involves sampling a sequence of data points in turn, before returning to the first data point. Hardware or software which performs commutation is referred to as a commutator; its opposite at the receiving end is a decommutator. Dedicated hardware generally supports faster commutation and decommutation than software on a general purpose architecture. Mechanism A set of Wor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commutation
Commute, commutation or commutative may refer to: * Commuting, the process of travelling between a place of residence and a place of work Mathematics * Commutative property, a property of a mathematical operation whose result is insensitive to the order of its arguments **Equivariant map, a function whose composition with another function has the commutative property ** Commutative diagram, a graphical description of commuting compositions of arrows in a mathematical category **Commutative semigroup, commutative monoid, abelian group, and commutative ring, algebraic structures with the commutative property **Commuting matrices, sets of matrices whose products do not depend on the order of multiplication ** Commutator, a measure of the failure of two elements to be commutative in a group or ring Science and technology * Commutator (electric), a rotary switch on the shaft of an electric motor or generator * Commutation (neurophysiology), how certain neural circuits in the brain ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telemetry
Telemetry is the in situ collection of measurements or other data at remote points and their automatic transmission to receiving equipment (telecommunication) for monitoring. The word is derived from the Greek roots ''tele'', "remote", and ''metron'', "measure". Systems that need external instructions and data to operate require the counterpart of telemetry, telecommand. Although the term commonly refers to wireless data transfer mechanisms (e.g., using radio, ultrasonic, or infrared systems), it also encompasses data transferred over other media such as a telephone or computer network, optical link or other wired communications like power line carriers. Many modern telemetry systems take advantage of the low cost and ubiquity of GSM networks by using SMS to receive and transmit telemetry data. A ''telemeter'' is a physical device used in telemetry. It consists of a sensor, a transmission path, and a display, recording, or control device. Electronic devices are widely ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frame (networking)
A frame is a digital data transmission unit in computer networking and telecommunication. In packet switched systems, a frame is a simple container for a single network packet. In other telecommunications systems, a frame is a repeating structure supporting time-division multiplexing. A frame typically includes frame synchronization features consisting of a sequence of bits or symbols that indicate to the receiver the beginning and end of the payload data within the stream of symbols or bits it receives. If a receiver is connected to the system during frame transmission, it ignores the data until it detects a new frame synchronization sequence. Packet switching In the OSI model of computer networking, a frame is the protocol data unit at the data link layer. Frames are the result of the final layer of encapsulation before the data is transmitted over the physical layer. A frame is "the unit of transmission in a link layer protocol, and consists of a link layer header followed by a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transmission (telecommunications)
In telecommunications, transmission is the process of sending or propagating an analog or digital signal via a medium that is wired, wireless, or fiber-optic. Transmission technologies typically refer to physical layer protocol duties such as modulation, demodulation, line coding, equalization, error control, bit synchronization and multiplexing, but it may also involve higher-layer protocol duties, for example, digitizing an analog signal, and data compression. Transmission of a digital message, or of a digitized analog signal, is known as data transmission. Examples of transmission are the sending of signals with limited duration, for example, a block or packet of data, a phone call, or an email. See also *Radio transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is appli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time-division Multiplexing
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern. This method transmits two or more digital signals or analog signals over a common channel. It can be used when the bit rate of the transmission medium exceeds that of the signal to be transmitted. This form of signal multiplexing was developed in telecommunications for telegraphy systems in the late 19th century, but found its most common application in digital telephony in the second half of the 20th century. History Time-division multiplexing was first developed for applications in telegraphy to route multiple transmissions simultaneously over a single transmission line. In the 1870s, Émile Baudot developed a time-multiplexing system of multiple Hughes telegraph machines. In 1944, the British ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frame Synchronization
In telecommunication, frame synchronization or framing is the process by which, while receiving a stream of framed data, incoming frame alignment signals (i.e., a distinctive bit sequences or syncwords) are identified (that is, distinguished from data bits), permitting the data bits within the frame to be extracted for decoding or retransmission. Framing If the transmission is temporarily interrupted, or a bit slip event occurs, the receiver must re-synchronize. The transmitter and the receiver must agree ahead of time on which frame synchronization scheme they will use. Common frame synchronization schemes are: ;Framing bit: A common practice in telecommunications, for example in T-carrier, is to insert, in a dedicated time slot within the frame, a noninformation bit or framing bit that is used for synchronization of the incoming data with the receiver. In a bit stream, framing bits indicate the beginning or end of a frame. They occur at specified positions in the frame, d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
L-3 Communications
L3 Technologies, formerly L-3 Communications Holdings, was an American company that supplied command and control, communications, intelligence, surveillance and reconnaissance ( C3ISR) systems and products, avionics, ocean products, training devices and services, instrumentation, aerospace, and navigation products. Its customers included the Department of Defense, Department of Homeland Security, United States Intelligence Community, NASA, aerospace contractors, and commercial telecommunications and wireless customers. In 2019, it merged with Harris Corporation and was renamed to L3Harris Technologies. L3 was headquartered in Murray Hill, Manhattan, New York City. History L3 was formed as L-3 Communications in 1997 to acquire certain business units from Lockheed Martin that had previously been part of Loral Corporation. These units had belonged to Lockheed Corporation and Martin Marietta, which had merged three years before in 1993. The company was founded by (and named for) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commutator (electric)
A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Two or more electrical contacts called "brushes" made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings (coils of wire) on the armature are connected to the commutator segments. Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors. In a motor the commutator applies electric current to the windings. By reversing the current direction in the rotating windings each half turn, a steady rotating force (torque) is produced. In a generator the commutator picks off the current generated in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Word (computer Architecture)
In computing, a word is the natural unit of data used by a particular processor design. A word is a fixed-sized datum handled as a unit by the instruction set or the hardware of the processor. The number of bits or digits in a word (the ''word size'', ''word width'', or ''word length'') is an important characteristic of any specific processor design or computer architecture. The size of a word is reflected in many aspects of a computer's structure and operation; the majority of the registers in a processor are usually word-sized and the largest datum that can be transferred to and from the working memory in a single operation is a word in many (not all) architectures. The largest possible address size, used to designate a location in memory, is typically a hardware word (here, "hardware word" means the full-sized natural word of the processor, as opposed to any other definition used). Documentation for older computers with fixed word size commonly states memory sizes in word ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance. A database management system (DBMS) is the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS software additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asynchronous Serial Communication
Asynchronous serial communication is a form of serial communication in which the communicating endpoints' interfaces are not continuously synchronized by a common clock signal. Instead of a common synchronization signal, the data stream contains synchronization information in form of start and stop signals, before and after each unit of transmission, respectively. The start signal prepares the receiver for arrival of data and the stop signal resets its state to enable triggering of a new sequence. A common kind of start-stop transmission is ASCII over RS-232, for example for use in teletypewriter operation. Origin Mechanical teleprinters using 5-bit codes (see Baudot code) typically used a stop period of 1.5 bit times.Dead link: 2015-Oct-03 Very early electromechanical teletypewriters (pre-1930) could require 2 stop bits to allow mechanical impression without buffering. Hardware which does not support fractional stop bits can communicate with a device that uses 1.5 bit tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serialization
In computing, serialization (or serialisation) is the process of translating a data structure or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e.g. data streams over computer networks) and reconstructed later (possibly in a different computer environment). When the resulting series of bits is reread according to the serialization format, it can be used to create a semantically identical clone of the original object. For many complex objects, such as those that make extensive use of references, this process is not straightforward. Serialization of object-oriented objects does not include any of their associated methods with which they were previously linked. This process of serializing an object is also called marshalling an object in some situations. The opposite operation, extracting a data structure from a series of bytes, is deserialization, (also called unserialization or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
