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71-471: The NASCOM network comprises microwave links , undersea communications cables , land lines , and network centers at Goddard and around the world. Prior to the advent of NASCOM, the Minitrack network—used to track the flights of Sputnik , Vanguard , Explorer , and other early spacecraft—largely relied on military-supplied teletype lines which were limited to about 30 bits per second. Scientific data from

142-419: A beam of radio waves in the microwave frequency range to transmit video , audio , or data between two locations, which can be from just a few feet or meters to several miles or kilometers apart. Microwave links are commonly used by television broadcasters to transmit programmes across a country, for instance, or from an outside broadcast back to a studio. Mobile units can be camera mounted, allowing cameras

213-528: A connection between New York City and Murray Hill, the location of Bell Laboratories in 1946. The TDX system was set up between New York and Boston in 1947. The TDX was upgraded to the TD2 system, which used [the Morton tube, 416B and later 416C, manufactured by Western Electric] in the transmitters, and then later to TD3 that used solid-state electronics . Remarkable were the microwave relay links to West Berlin during

284-419: A diameter of up to 4 m (13 ft). Highly directive antennas permit an economical use of the available frequency spectrum, despite long transmission distances. Because of the high frequencies used, a line-of-sight path between the stations is required. Additionally, in order to avoid attenuation of the beam, an area around the beam called the first Fresnel zone must be free from obstacles. Obstacles in

355-413: A distance of 56 km (35 miles), was followed in 1935 by a 300 MHz telecommunication link, the first commercial microwave relay system. The development of radar during World War II provided much of the microwave technology which made practical microwave communication links possible, particularly the klystron oscillator and techniques of designing parabolic antennas. Though not commonly known,

426-488: A few kilometers, not enough for long-distance communication. The electronic technologies needed in the millimeter wave band are also in an earlier state of development than those of the microwave band. More recently, microwaves have been used for wireless power transmission . Microwave radio relay is a technology widely used in the 1950s and 1960s for transmitting information, such as long-distance telephone calls and television programs between two terrestrial points on

497-522: A less expensive IBM 7044 to handle input/output (I/O) with the 7094 performing mostly computation. Aerospace developed the Direct Couple operating system, an extension to IBSYS, which was shared with other IBM customers. IBM later introduced the DCS as a product. The 7090 used more than 50,000 germanium alloy-junction transistors and (faster) germanium diffused junction drift transistors . The 7090 used

568-530: A line of sight limits the separation between stations to the visual horizon, about 30 to 50 miles (48 to 80 km). For longer distances, the receiving station could function as a relay, retransmitting the received information to another station along its journey. Chains of microwave relay stations were used to transmit telecommunication signals over transcontinental distances. Microwave relay stations were often located on tall buildings and mountaintops, with their antennas on towers to get maximum range. Beginning in

639-569: A lower cost per bit. During the Cold War, the US intelligence agencies, such as the National Security Agency (NSA), were reportedly able to intercept Soviet microwave traffic using satellites such as Rhyolite/Aquacade . Much of the beam of a microwave link passes the receiving antenna and radiates toward the horizon, into space. By positioning a geosynchronous satellite in the path of the beam,

710-463: A month (equivalent to $ 501,000 in 2023). The 7090 uses a 36-bit word length , with an address space of 32,768 words (15-bit addresses). It operates with a basic memory cycle of 2.18 μs, using the IBM 7302 Core Storage core memory technology from the IBM 7030 (Stretch) project. With a processing speed of around 100 Kflop/s , the 7090 is six times faster than the 709, and could be rented for half

781-487: A narrow beam of microwaves. In microwave radio relay, a microwave transmitter and directional antenna transmits a narrow beam of microwaves carrying many channels of information on a line of sight path to another relay station where it is received by a directional antenna and receiver, forming a fixed radio connection between the two points. The link was often bidirectional, using a transmitter and receiver at each end to transmit data in both directions. The requirement of

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852-655: A voice network and a teletype network on separate channels, each with a backup channel. The teletype network, based on the Western Union Type 111 Torn-Tape Relay System, did not offer any speed improvement over the Minitrack network, though it allowed switching based on coded addresses. A data trunk was established between Goddard and Cape Canaveral, with four voice-bandwidth circuits each capable of carrying 1000 bits per second. Later, voice-band links were established from STADAN ground stations and Bermuda. The Mercury Network

923-645: A wide variety of software provided for them by IBM. In addition, there was a very active user community within the user organization, SHARE . IBSYS is a "heavy duty" production operating system with numerous subsystem and language support options, among them FORTRAN , COBOL , SORT/MERGE, the MAP assembler, and others. FMS, the Fortran Monitor System , was a more lightweight but still very effective system optimized for batch FORTRAN and assembler programming. The assembler provided, FAP, ( FORTRAN Assembly Program ),

994-604: A wider effort to standardize communications among federal agencies (the National Communications System), in response to difficulties that arose during the Cuban Missile Crisis . The Gemini Program introduced digital encoding to what would become the NASCOM network, enabling convergence among NASA's disparate networks. Between 1964 and 1966, several other advances were made to the network, largely to support

1065-487: Is a second-generation transistorized version of the earlier IBM 709 vacuum tube mainframe computer that was designed for "large-scale scientific and technological applications". The 7090 is the fourth member of the IBM 700/7000 series scientific computers. The first 7090 installation was in December 1959. In 1960, a typical system sold for $ 2.9 million (equivalent to $ 23 million in 2023) or could be rented for $ 63,500

1136-408: Is regulated by International Telecommunication Union ( ITU-R ) and local regulations ( ETSI , FCC ). In the last decade the dedicated spectrum for each microwave band has become extremely crowded, motivating the use of techniques to increase transmission capacity such as frequency reuse, polarization-division multiplexing , XPIC , MIMO . The history of radio relay communication began in 1898 with

1207-645: The CCSDS Space Link Extension service. As of 2007, NASCOM data blocks were considered a "legacy" protocol, and continued to be encapsulated in IP packets for transmission on the NASA Integrated Services Network (NISN). Microwave link Microwave transmission is the transmission of information by electromagnetic waves with wavelengths in the microwave frequency range of 300 MHz to 300 GHz (1 m - 1 mm wavelength) of

1278-554: The Cold War , which had to be built and operated due to the large distance between West Germany and Berlin at the edge of the technical feasibility. In addition to the telephone network, also microwave relay links for the distribution of TV and radio broadcasts. This included connections from the studios to the broadcasting systems distributed across the country, as well as between the radio stations, for example for program exchange. Military microwave relay systems continued to be used into

1349-483: The English Channel using 10-foot (3 m) dishes. Telephony, telegraph, and facsimile data was transmitted over the bidirectional 1.7 GHz beams 40 miles (64 km) between Dover , UK, and Calais , France. The radiated power, produced by a miniature Barkhausen–Kurz tube located at the dish's focus, was one-half watt. A 1933 military microwave link between airports at St. Inglevert, France, and Lympne, UK,

1420-750: The English Channel was demonstrated in 1931, the development of radar in World War II provided the technology for practical exploitation of microwave communication. During the war, the British Army introduced the Wireless Set No. 10, which used microwave relays to multiplex eight telephone channels over long distances. A link across the English Channel allowed General Bernard Montgomery to remain in continual contact with his group headquarters in London. In

1491-441: The IBM 1403 line printer. Later IBM introduced the 7094/7044 Direct Coupled System ; the 7044 handled spooling between its fast 1400-series peripherals and 1301 or 1302 disk files, and used data channel to data channel communication as the 7094's interface to spooled data, with the 7094 primarily performing computations. There is also a 7090/7040 DCS. The 7090 and 7094 machines were quite successful for their time, and had

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1562-546: The IBM 7040 and 7044. They have a 36-bit architecture based on the 7090, but with some instructions omitted or optional, and simplified input/output that allows the use of more modern, higher performance peripherals from the IBM 1400 series . The 7094/7044 Direct Coupled System (DCS) was initially developed by an IBM customer, the Aerospace Corporation , seeking greater cost efficiency and scheduling flexibility than IBM's IBSYS tape operating system provided. DCS used

1633-465: The Standard Modular System (SMS) cards using current-mode logic some using diffused junction drift transistors. The basic instruction formats were the same as the IBM 709 : The documentation of opcodes used signed octal. The flag field indicated whether to use indirect addressing or not. The decrement field often contained an immediate operand to modify the results of the operation, or

1704-483: The electromagnetic spectrum . Microwave signals are normally limited to the line of sight , so long-distance transmission using these signals requires a series of repeaters forming a microwave relay network. It is possible to use microwave signals in over-the-horizon communications using tropospheric scatter , but such systems are expensive and generally used only in specialist roles. Although an experimental 40-mile (64 km) microwave telecommunication link across

1775-400: The 1950s a unit of the US telephone carrier, AT&T Long Lines , built a transcontinental system of microwave relay links across the US which grew to carry the majority of US long distance telephone traffic, as well as television network signals. The main motivation in 1946 to use microwave radio instead of cable was that a large capacity could be installed quickly and at less cost. It

1846-611: The 1950s, networks of microwave relay links, such as the AT&;T Long Lines system in the U.S., carried long-distance telephone calls and television programs between cities. The first system, dubbed TDX and built by AT&T, connected New York and Boston in 1947 with a series of eight radio relay stations. Through the 1950s, they deployed a network of a slightly improved version across the U.S., known as TD2 . These included long daisy-chained links that traversed mountain ranges and spanned continents. The launch of communication satellites in

1917-485: The 1960s, when many of these systems were supplanted with tropospheric scatter or communication satellite systems. When the NATO military arm was formed, much of this existing equipment was transferred to communications groups. The typical communications systems used by NATO during that time period consisted of the technologies which had been developed for use by the telephone carrier entities in host countries. One example from

1988-824: The 1970s and 80s, and the introduction of long-distance fibre optic systems in the 1980s and especially 90s led to the rapid rundown of the relay networks, most of which are abandoned. In recent years, there has been an explosive increase in use of the microwave spectrum by new telecommunication technologies such as wireless networks , and direct-broadcast satellites which broadcast television and radio directly into consumers' homes. Larger line-of-sight links are once again popular for handing connections between mobile telephone towers, although these are generally not organized into long relay chains. Microwaves are widely used for point-to-point communications because their small wavelength allows conveniently-sized antennas to direct them in narrow beams, which can be pointed directly at

2059-411: The 1970s provided a cheaper alternative. Much of the transcontinental traffic is now carried by satellites and optical fibers , but microwave relay remains important for shorter distances. Because in microwave transmission the waves travel in narrow beams confined to a line-of-sight path from one antenna to the other, they do not interfere with other microwave equipment, so nearby microwave links can use

2130-626: The 1990s. By 1995, NASCOM was the largest of five wide area networks operated by NASA, with 900 leased circuits and a budget of $ 63 million. It employed 21 civil servants and 210 contracted personnel under two contracts. Soon after, NASA undertook an effort to consolidate these networks, in order to realize cost savings. In its FY 1995 Nascom System Development Plan, the NASA Communications Division underwent reorganization, with contractors taking over operations and maintenance roles previously performed by civil servants. The plan expressed

2201-406: The 1990s. Frequency bands below 10 GHz, and above all, the information to be transmitted, were a stream containing a fixed capacity block. The target was to supply the requested availability for the whole block ( Plesiochronous digital hierarchy , PDH, or synchronous digital hierarchy , SDH). Fading and/or multipath affecting the link for short time period during the day had to be counteracted by

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2272-599: The 7070 and other 7000 series equipment were sometimes called by names of digit - digit - decade (e.g., seven - oh - seventy). An upgraded version, the IBM 7094 , was first installed in September 1962. It has seven index registers , instead of three on the earlier machines. The 7151-2 Console Control Unit for the 7094 has a distinctive box on top that displays lights for the four new index registers. The 7094 introduced double-precision floating point and additional instructions , but largely maintained backward compatibility with

2343-480: The 7090. Although the 7094 has four more index registers than the 709 and 7090, at power-on time it is in multiple tag mode , compatible with the 709 and 7090, and requires a Leave Multiple Tag Mode instruction in order to enter seven index register mode and use all seven index registers. In multiple tag mode, when more than one bit is set in the tag field, the contents of the two or three selected index registers are logically ORed , not added , together, before

2414-550: The Apollo tracking ships . Two of these spacecraft launched successfully, and began to handle commercial traffic in addition to supporting Apollo. Throughout the Apollo Program, incremental improvements to NASCOM continued. High-speed data terminals were implemented across the world, new communications control centers and backup centers were established, lines were upgraded to support higher data rates, DSN stations were integrated into

2485-524: The British Army used the Wireless Set Number 10 in this role during World War II. The need for radio relay did not really begin until the 1940s exploitation of microwaves , which traveled by line of sight and so were limited to a propagation distance of about 40 miles (64 km) by the visual horizon. After the war, telephone companies used this technology to build large microwave radio relay networks to carry long-distance telephone calls. During

2556-644: The Mercury Network were issued on May 21, 1959, establishing a baseline with a mission control center in Cape Canaveral (later Houston ), data convergence at Goddard, and switching stations overseas to provide redundancy and trunking over expensive transoceanic cables. These decisions would shape NASCOM for years to follow. The Mercury network was designed by the Tracking and Ground Instrumentation Unit (TAGIU) at Langley , with support from Goddard. It consisted of

2627-531: The USA is the RCA CW-20A 1–2 GHz microwave relay system which utilized flexible UHF cable rather than the rigid waveguide required by higher frequency systems, making it ideal for tactical applications. The typical microwave relay installation or portable van had two radio systems (plus backup) connecting two line of sight sites. These radios would often carry 24 telephone channels frequency-division multiplexed on

2698-571: The Vanguard missions was recorded at ground stations onto magnetic tape , and air mailled to the control center at the Naval Research Laboratory . This reliance on military lines and stations undermined somewhat the purely scientific climate that the Navy and NASA sought to promote. As NASA developed more advanced satellites in the early 1960s, the capability for telecommand grew, and Minitrack

2769-667: The administration of the recently formed Office of Tracking and Data Acquisition. NASCOM tied together NASA's three tracking and acquisition networks at the time: the Spacecraft Tracking and Data Acquisition Network (STADAN), the Manned Space Flight Network (MSFN), and the Deep Space Network (DSN). Manned missions, beginning with Project Mercury in 1958, demanded a real-time voice circuit in addition to data circuits, and improved reliability. Specifications for

2840-400: The area and reception issues arising from the use of nearby land (such as in manufacturing and forestry) are important issues to consider when planning radio links. In the planning process, it is essential that "path profiles" are produced, which provide information about the terrain and Fresnel zones affecting the transmission path. The presence of a water surface, such as a lake or river, along

2911-584: The decrement takes place. In seven index register mode, if the three-bit tag field is not zero, it selects just one of seven index registers, however, the program can return to multiple tag mode with the instruction Enter Multiple Tag Mode , restoring 7090 compatibility. In April 1964, the first 7094 II was installed, which had almost twice as much general speed as the 7094 due to a faster clock cycle , dual memory banks and improved overlap of instruction execution, an early instance of pipelined design. In 1963, IBM introduced two new, lower cost machines called

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2982-641: The demands of crewed missions. Torn-tape and electromechanical switching systems were replaced with solid state , automated systems, and the switching center at Goddard was redesigned to improve reliability and capacity, using IBM 7094 and UNIVAC 490 computers. Voice capability was expanded to all MSFN, DSN, and other sites, and multiplexing of teletype messages was introduced at overseas switching centers. The Apollo Program demanded augmentation of NASCOM lines to handle increased communication traffic, including television signals. By 1969, 2.0 million miles (3.2 million km) of circuits had been laid. By 1974, NASCOM

3053-860: The detrimental factors mentioned in this section, collectively known as path loss , make it necessary to compute suitable power margins, in order to maintain the link operative for a high percentage of time, like the standard 99.99% or 99.999% used in 'carrier class' services of most telecommunication operators. The longest known microwave radio relay crosses the Red Sea with a 360 km (220 mi) hop between Jebel Erba (2,170 m (7,120 ft) a.s.l., 20°44′46.17″N 36°50′24.65″E  /  20.7461583°N 36.8401806°E  / 20.7461583; 36.8401806 , Sudan) and Jebel Dakka (2,572 m (8,438 ft) a.s.l., 21°5′36.89″N 40°17′29.80″E  /  21.0935806°N 40.2916111°E  / 21.0935806; 40.2916111 , Saudi Arabia). The link

3124-542: The diversity architecture. During 1990s microwave radio links begun widely to be used for urban links in cellular network . Requirements regarding link distance changed to shorter hops (less than 10 km (6.2 mi), typically 3 to 5 km (1.9 to 3.1 mi)), and frequency increased to bands between 11 and 43 GHz and more recently, up to 86 GHz (E-band). Furthermore, link planning deals more with intense rainfall and less with multipath, so diversity schemes became less used. Another big change that occurred during

3195-414: The freedom to move around without trailing cables. These are often seen on the touchlines of sports fields on Steadicam systems. Terrestrial microwave relay links are limited in distance to the visual horizon, a few tens of miles or kilometers depending on tower height. Tropospheric scatter ("troposcatter" or "scatter") was a technology developed in the 1950s to allow microwave communication links beyond

3266-453: The horizon, to a range of several hundred kilometers. The transmitter radiates a beam of microwaves into the sky, at a shallow angle above the horizon toward the receiver. As the beam passes through the troposphere a small fraction of the microwave energy is scattered back toward the ground by water vapor and dust in the air. A sensitive receiver beyond the horizon picks up this reflected signal. Signal clarity obtained by this method depends on

3337-420: The last decade was an evolution toward packet radio transmission. Therefore, new countermeasures, such as adaptive modulation , have been adopted. The emitted power is regulated for cellular and microwave systems. These microwave transmissions use emitted power typically from 0.03 to 0.30 W, radiated by a parabolic antenna on a narrow beam diverging by a few degrees (1 to 3-4). The microwave channel arrangement

3408-514: The microwave band has a bandwidth 30 times that of all the rest of the radio spectrum below it. A disadvantage is that microwaves are limited to line of sight propagation; they cannot pass around hills or mountains as lower frequency radio waves can. Microwave radio transmission is commonly used in point-to-point communication systems on the surface of the Earth, in satellite communications , and in deep space radio communications . Other parts of

3479-409: The microwave beam can be received. At the turn of the century, microwave radio relay systems were used increasingly in portable radio applications. The technology is particularly suited to this application because of lower operating costs, a more efficient infrastructure , and provision of direct hardware access to the portable radio operator. A microwave link is a communications system that uses

3550-438: The microwave carrier (i.e. Lenkurt 33C FDM). Any channel could be designated to carry up to 18 teletype communications instead. Similar systems from Germany and other member nations were also in use. Long-distance microwave relay networks were built in many countries until the 1980s, when the technology lost its share of fixed operation to newer technologies such as fiber-optic cable and communication satellites , which offer

3621-458: The microwave radio band are used for radars , radio navigation systems, sensor systems, and radio astronomy . The next higher frequency band of the radio spectrum , between 30 GHz and 300 GHz, are called " millimeter waves " because their wavelengths range from 10 mm to 1 mm. Radio waves in the millimeter wave band are strongly attenuated by the gases of the atmosphere , which limits their practical transmission distance to

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3692-448: The need to convert to standardized network systems. With the advent of modern packet-switched networks, a custom tunneling protocol was created to support continued use of NASCOM's 1200-bit and 4800-bit data block point-to-point format; requiring custom hardware and software. NASA announced a plan to eliminate the need for the 4800-bit data block protocol by 1997. In 2002, NASA funded an investigation into replacing NASCOM data blocks with

3763-416: The path also must be taken into consideration since it can reflect the beam, and the direct and reflected beam can interfere with each other at the receiving antenna, causing multipath fading. Multipath fades are usually deep only in a small spot and a narrow frequency band, so space and/or frequency diversity schemes can be applied to mitigate these effects. The effects of atmospheric stratification cause

3834-487: The post-war era, the development of microwave technology was rapid, which led to the construction of several transcontinental microwave relay systems in North America and Europe. In addition to carrying thousands of telephone calls at a time, these networks were also used to send television signals for cross-country broadcast, and later, computer data. Communication satellites took over the television broadcast market during

3905-453: The price. An upgraded version, the 7094, was up to twice as fast. Both the 7090 and the 7094 were withdrawn from sale on July 14, 1969, but systems remained in service for more than a decade after. In 1961, the IBM 7094 famously employed a speech synthesis program to sing " Daisy Bell ", becoming something of a cultural icon . Although the 709 was a superior machine to its predecessor, the 704, it

3976-648: The publication by Johann Mattausch in the Austrian journal, Zeitschrift für Elektrotechnik. But his proposal was primitive and not suitable for practical use. The first experiments with radio repeater stations to relay radio signals were done in 1899 by Emile Guarini-Foresio. However the low frequency and medium frequency radio waves used during the first 40 years of radio proved to be able to travel long distances by ground wave and skywave propagation. In 1931, an Anglo-French consortium headed by Andre C. Clavier demonstrated an experimental microwave relay link across

4047-556: The radio path to bend downward in a typical situation so a major distance is possible as the earth equivalent curvature increases from 6,370 km (3,960 mi) to about 8,500 km (5,300 mi) (a 4/3 equivalent radius effect). Rare events of temperature, humidity and pressure profile versus height, may produce large deviations and distortion of the propagation and affect transmission quality. High-intensity rain and snow making rain fade must also be considered as an impairment factor, especially at frequencies above 10 GHz. All of

4118-408: The receiving antenna. This use of tightly-focused direct beams allows microwave transmitters in the same area to use the same frequencies, without interfering with each other as lower frequency radio waves would. This frequency reuse conserves scarce radio spectrum bandwidth. Another advantage is that the high frequency of microwaves gives the microwave band a very large information-carrying capacity;

4189-407: The same frequencies. The antennas must therefore be highly directional (high gain ), and are installed in elevated locations such as large radio towers in order to be able to avoid the obstructions closer to the ground and transmit across long distances. Typical types of antenna used in radio relay link installations are parabolic antennas , dielectric lens, and horn-reflector antennas , which have

4260-403: The signal field cause unwanted attenuation . High mountain peaks or ridges are often ideal positions for the antennas. In addition to the use of conventional repeaters with back-to-back radios transmitting on different frequencies, obstructions in microwave paths can also be dealt with by using Passive repeater or on-frequency repeaters. Obstacles, the curvature of the Earth, the geography of

4331-578: The teletype switching system, and a video control center was stood up in Sydney to switch between antennas and process color signals for television broadcast. In July 1967, the Tracking and Data Systems Directorate was split, and NASCOM became part of the new Manned Spaceflight Support Directorate. By 1983, NASCOM included 139 stations and 630 circuits, including satellite links, covering more than 2.5 million miles (4.0 million km), with nearly all of this circuitry leased . NASCOM network development continued in

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4402-401: The time. Printing and punched card I/O, however, employed the same modified unit record equipment introduced with the 704 and was slow. It became common to use a less expensive IBM 1401 computer to read cards onto magnetic tape for transfer to the 7090/94. Output would be written onto tape and transferred to the 1401 for printing or card punching using its much faster peripherals, notably

4473-986: The weather and other factors, and as a result, a high level of technical difficulty is involved in the creation of a reliable over horizon radio relay link. Troposcatter links are therefore only used in special circumstances where satellites and other long-distance communication channels cannot be relied on, such as in military communications. ELF 3 Hz/100 Mm 30 Hz/10 Mm SLF 30 Hz/10 Mm 300 Hz/1 Mm ULF 300 Hz/1 Mm 3 kHz/100 km VLF 3 kHz/100 km 30 kHz/10 km LF 30 kHz/10 km 300 kHz/1 km MF 300 kHz/1 km 3 MHz/100 m HF 3 MHz/100 m 30 MHz/10 m VHF 30 MHz/10 m 300 MHz/1 m UHF 300 MHz/1 m 3 GHz/100 mm SHF 3 GHz/100 mm 30 GHz/10 mm EHF 30 GHz/10 mm 300 GHz/1 mm THF 300 GHz/1 mm 3 THz/0.1 mm IBM 7094 The IBM 7090

4544-751: Was an indirect effective address ; i.e., fetch the word at that location and treat the T and Y fields as described above. Data formats are Octal notation was used in documentation and programming; console displays lights and switches were grouped into three-bit fields for easy conversion to and from octal. The 7090 series features a data channel architecture for input and output, a forerunner of modern direct memory access I/O. Up to eight data channels can be attached, with up to ten IBM 729 tape drives attached to each channel. The data channels have their own very limited set of operations called commands. These are used with tape (and later, disk) storage as well as card units and printers, and offered high performance for

4615-407: Was being built and sold at the time that transistor circuitry was supplanting vacuum tube circuits. Hence, IBM redeployed its 709 engineering group to the design of a transistorized successor. That project became called the 709-T (for transistorized ), which because of the sound when spoken, quickly shifted to the nomenclature 7090 (i.e., seven - oh - ninety). Similarly, the related machines such as

4686-445: Was built in 1979 by Telettra to transmit 300 telephone channels and one TV signal, in the 2 GHz frequency band. (Hop distance is the distance between two microwave stations). Previous considerations represent typical problems characterizing terrestrial radio links using microwaves for the so-called backbone networks: hop lengths of a few tens of kilometers (typically 10 to 60 km (6.2 to 37.3 mi)) were largely used until

4757-452: Was designed under significant time pressure, and integration of the new circuits with the existing Minitrack network was a low priority. Minitrack, Mercury, and JPL networks would eventually be integrated, albeit slowly; an integrated communications division was formed at Goddard in July 1963 to coordinate all NASA ground communications, in what became known as NASCOM. This consolidation was part of

4828-413: Was expected at that time that the annual operating costs for microwave radio would be greater than for cable. There were two main reasons that a large capacity had to be introduced suddenly: Pent-up demand for long-distance telephone service, because of the hiatus during the war years, and the new medium of television, which needed more bandwidth than radio. The prototype was called TDX and was tested with

4899-543: Was no longer sufficient. Later, as NASA recruited personnel from military and industry, it began to accrue an in-house knowledge base for wide-band, real-time computer-based networks. Network technologies used in NORAD and the Semi-Automatic Ground Environment (SAGE) defense system contributed to the development of NASCOM. NASCOM began taking shape in the early 1960s, and was formally established in 1964, under

4970-539: Was the largest broad-band , real-time communication network in the world, linking all the continents except for Asia and Antarctica, and allowing for a two-way "dialog" with spacecraft from a centralized mission control center. Notably, Apollo also spurred the development of communications satellites . In June 1965, NASA engaged the Communications Satellite Corporation (COMSAT) to launch three geosynchronous satellites to support communication with

5041-411: Was used to further define the instruction type. The tag field might describe an index register to be operated on, or be used as described below. The Y field might contain an address, an immediate operand or an opcode modifier. For instructions where the tag field indicated indexing, the operation was If there was no F field or F is not all one bits, then the above was the effective address . Otherwise it

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