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SITOR-B
SITOR (SImplex Teletype Over Radio) is a system for transmitting text messages. It was developed in the 1960s by Koninklijke TNT Post as an improvement over radioteletype (RTTY). Although it uses the same frequency-shift keying (FSK) modulation used by regular RTTY, SITOR uses error detection, redundancy, and/or retransmission to improve reliability. There are two SITOR modes: * SITOR-A is used for point to point links. SITOR-A uses automatic repeat request (ARQ) to gain reliability. If the receiver detects an error, it requests a retransmission. * SITOR-B is used for broadcast links. SITOR-B transmits each character in a message twice to gain reliability. If the receiver detects an error in the first character, it uses the copy. If both characters are garbled, the receiver won't know what was sent. * SITOR-B by definition uses forward error correction (FEC), versus ARQ for SITOR-A. SITOR sends 7-bit characters as a bit stream at 100 baud (which, in this case, is 100 bits per se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NAVTEX
NAVTEX (NAVigational TEleX), sometimes styled Navtex or NavTex, is an international automated medium frequency direct-printing service for delivery of navigational and meteorological warnings and forecasts, as well as urgent maritime safety information (MSI) to ships. NAVTEX was developed in the late 1970s in northwestern Europe to provide a low-cost, simple, and automated means of receiving this information aboard ships at sea within approximately off-shore. There are no user fees associated with receiving NAVTEX broadcasts, as the transmissions are typically transmitted from the National Weather Authority (Italy) or Navy or Coast Guard (as in the US) or national navigation authority (Canada). Where the messages contain weather forecasts, an abbreviated format very similar to the shipping forecast is used. NAVTEX is a component of the International Maritime Organization/International Hydrographic Organization Worldwide Navigation Warning Service (WWNWS). NAVTEX is also a m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amateur Radio
Amateur radio, also known as ham radio, is the use of the radio frequency radio spectrum, spectrum for purposes of non-commercial exchange of messages, wireless experimentation, self-training, private recreation, radiosport, contesting, and emergency, emergency communications. The term ''"radio amateur"'' is used to specify ''"a duly authorized person interested in radioelectric practice with a purely personal aim and without wikt:pecuniary, pecuniary interest"'' (either direct monetary or other similar reward); and to differentiate it from commercial broadcasting, public safety (police and fire), or two-way radio professional services (maritime, aviation, taxis, etc.). The amateur radio service (''amateur service'' and ''amateur-satellite service'') is established by the International Telecommunication Union (ITU) through their recommended radio regulations. National governments regulate technical and operational characteristics of transmissions and issue individual station li ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synchronization Burst
In computer networks, a syncword, sync character, sync sequence or preamble is used to synchronize a data transmission by indicating the end of header information and the start of data. The syncword is a known sequence of data used to identify the start of a frame, and is also called ''reference signal'' or ''midamble'' in wireless communications. Prefix codes allow unambiguous identification of synchronization sequences and may serve as self-synchronizing code. Examples In an audio receiver receiving a bit stream of data, an example of a syncword is 0x0B77 for an AC-3 encoded stream. An Ethernet packet with the Ethernet preamble, 56 bits of alternating 1 and 0 bits, allowing the receiver to synchronize its clock to the transmitter, followed by a one-octet start frame delimiter byte and then the header. All USB packets begin with a sync field (8 bits long at low speed, 32 bits long at high speed) used to synchronize the receiver's clock to the transmitter's clock. A rece ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Point Reyes
Point Reyes ( , meaning 'Cape of the Kings') is a prominent landform and popular tourist destination on the Pacific coast of Marin County in Northern California. It is approximately west-northwest of San Francisco. The term is often applied to the Point Reyes Peninsula, the region bounded by Tomales Bay on the northeast and Bolinas Lagoon on the southeast. The majority of the peninsula as well as the headlands are protected as part of Point Reyes National Seashore. Overview The cape protects Drakes Bay on its southern side. The headland is largely drained by Drakes Estero. Drakes Bay and Drake's Estero are named after English seafarer Sir Francis Drake who possibly hauled his ship, the '' Golden Hinde'', up onto the beach for repairs in June 1579. Inverness Ridge runs along the peninsula's northwest-southeast spine, with forested peaks around . West of the ridge, the land flattens out and the vegetation turns to scrub. The Mount Vision fire in 1995 burned part of I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Binomial Coefficient
In mathematics, the binomial coefficients are the positive integers that occur as coefficients in the binomial theorem. Commonly, a binomial coefficient is indexed by a pair of integers and is written \tbinom. It is the coefficient of the term in the polynomial expansion of the binomial power ; this coefficient can be computed by the multiplicative formula : \binom nk = \frac, which using factorial notation can be compactly expressed as : \binom = \frac. For example, the fourth power of is : \begin (1 + x)^4 &= \tbinom x^0 + \tbinom x^1 + \tbinom x^2 + \tbinom x^3 + \tbinom x^4 \\ &= 1 + 4x + 6 x^2 + 4x^3 + x^4, \end and the binomial coefficient \tbinom =\tfrac = \tfrac = 6 is the coefficient of the term. Arranging the numbers \tbinom, \tbinom, \ldots, \tbinom in successive rows for gives a triangular array called Pascal's triangle, satisfying the recurrence relation : \binom = \binom + \binom . The binomial coefficients occur in many areas of mathematics, and espe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hamming Distance
In information theory, the Hamming distance between two String (computer science), strings or vectors of equal length is the number of positions at which the corresponding symbols are different. In other words, it measures the minimum number of ''substitutions'' required to change one string into the other, or equivalently, the minimum number of ''errors'' that could have transformed one string into the other. In a more general context, the Hamming distance is one of several string metrics for measuring the edit distance between two sequences. It is named after the American mathematician Richard Hamming. A major application is in coding theory, more specifically to block codes, in which the equal-length strings are Vector space, vectors over a finite field. Definition The Hamming distance between two equal-length strings of symbols is the number of positions at which the corresponding symbols are different. Examples The symbols may be letters, bits, or decimal digits, am ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CCIR 476
CCIR 476 is a character encoding used in radio data protocols such as SITOR, AMTOR and Navtex. It is a recasting of the ITA2 character encoding, known as Baudot code, from a five-bit code to a seven-bit code. In each character, exactly four of the seven bits are mark bits, and the other three are space bits. This allows for the detection of single-bit errors. Technical details The number of possible valid binary code values in CCIR 476 is the number of ways to choose 4 marks for 7 bit positions, and the number can be calculated using the binomial coefficient: \ \textstyle \binom = \binom = 35\ . Thus CCIR 476 has 3 additional code points available over ITA2's 32 code points. The SITOR SITOR (SImplex Teletype Over Radio) is a system for transmitting text messages. It was developed in the 1960s by Koninklijke TNT Post as an improvement over radioteletype (RTTY). Although it uses the same frequency-shift keying (FSK) modulation use ... protocol uses th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cross Pattée
A cross pattée or cross patty (, ), also known as a cross formée or cross formy, or even a Templar cross, is a type of Christian cross with arms that are narrow at the centre and often flared in a curve or straight line shape to be broader at the perimeter. The form appears very early in medieval art, for example, in a metalwork treasure binding given to Monza Cathedral by Lombards, Lombard queen Theodelinda (died 628) and the 8th-century lower cover of the Lindau Gospels in the Morgan Library. An early English example from the start of the age of heraldry proper (i.e., about 1200) is found in the arms of Baron Berkeley. Etymology The word ''pattée'' is a French language, French adjective in the feminine form used in its full context as ''la croix pattée'', meaning literally "footed cross", from the noun ''patte'', meaning literally foot, generally that of an animal. The cross has four splayed feet, each akin to the foot, for example, of a chalice or candelabrum. In German la ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Code Point
A code point, codepoint or code position is a particular position in a Table (database), table, where the position has been assigned a meaning. The table may be one dimensional (a column), two dimensional (like cells in a spreadsheet), three dimensional (sheets in a workbook), etc... in any number of dimensions. Technically, a code point is a unique position in a quantized n-dimensional space, where the position has been assigned a semantic meaning. The table has discrete (whole) and positive positions (1, 2, 3, 4, but not fractions). Code points are used in a multitude of formal information processing and telecommunication standards.ETSI TS 101 773 (section 4), https://www.etsi.org/deliver/etsi_ts/101700_101799/101773/01.02.01_60/ts_101773v010201p.pdf For example ITU-T Recommendation T.35 contains a set of country codes for telecommunications equipment (originally fax machines) which allow equipment to indicate its country of manufacture or operation. In T.35, Argentina is repre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baudot Code
The Baudot code () is an early character encoding for telegraphy invented by Émile Baudot in the 1870s. It was the predecessor to the International Telegraph Alphabet No. 2 (ITA2), the most common teleprinter code in use before ASCII. Each character in the alphabet is represented by a series of five bits, sent over a communication channel such as a telegraph wire or a radio signal by asynchronous serial communication. The symbol rate measurement is known as baud, and is derived from the same name. History Baudot code (ITA1) In the below table, Columns I, II, III, IV, and V show the code; the Let. and Fig. columns show the letters and numbers for the Continental and UK versions; and the sort keys present the table in the order: alphabetical, Gray and UK Baudot developed his first multiplexed telegraph in 1872 [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AMTOR
The Venus series (or Amtor series) is a science fantasy series consisting of four novels and one novelette written by American author Edgar Rice Burroughs. Most of the stories were first serialized in '' Argosy'', an American pulp magazine. It is sometimes known as the Carson Napier of Venus series, after its main character, Carson Napier. Napier attempted a solo voyage to Mars, but, because of mistaken navigational calculations, he finds himself heading toward the planet Venus instead. The novels, part of the sword and planet subgenre of science fiction, follow earthman Napier's fantastic adventures after he crash-lands on Venus, called Amtor by its human-like inhabitants. Unlike Barsoom, the desert planet of Mars, these stories are set upon a waterworld like Earth. Most of the events of the series take place on the island of Vepaja, the kingdom of Korva on the island of Anlap, and the city-states of Havatoo and Kormor on the tropical continent north of Vepaja. As is common in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Simplex Communication
A duplex communication system is a Point-to-point (telecommunications), point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow for simultaneous communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field. There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX). In a full-duplex system, both parties can communicate with each other simultaneously. An example of a full-duplex device is plain old telephone service; the parties at both ends of a call can speak and be heard by the other party simultaneously. The earphone reproduces the speech of the remote party as the microphone transmits the speech of the local party. There is a two-way communication channel between them, or more strictly speaking, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
