Nav Canada is a run, not-for-profit corporation that owns and operates Canada's civil air navigation system. It was established in accordance with the Civil Air Navigation Services Commercialization Act; the company employs 1,900 air traffic controllers, 650 flight service specialists and 700 technologists. It has been responsible for the safe and expeditious flow of air traffic in Canadian airspace since November 1, 1996 when the government transferred the ANS from Transport Canada to Nav Canada; as part of the transfer, or privatization, Nav Canada paid the government CA$1.5 billion. Nav Canada manages 12 million aircraft movements a year for 40,000 customers in over 18 million square kilometres, making it the world’s second-largest air navigation service provider by traffic volume. Nav Canada, which operates independently of any government funding, is headquartered in Ottawa, Ontario, it is only allowed to be funded by service charges to aircraft operators. Nav Canada's operations consist of various sites across the country.
These include: About 1,400 ground-based navigation aids 55 flight service stations 8 flight information centres, one each in: Kamloops – most of British Columbia Edmonton – all of Alberta and northeastern BC Winnipeg – northwestern Ontario, all of Manitoba and Saskatchewan London – most of Ontario North Bay – all of Nunavut and Northwest Territories, most of the Arctic waters Quebec City – all of Quebec, southwestern Labrador, tip of eastern Ontario, northern New Brunswick Halifax – most of New Brunswick, Nova Scotia, Prince Edward Island, most of Newfoundland and Labrador Whitehorse – northwestern British Columbia and all of Yukon 41 control towers 46 radar sites and 15 automatic dependent surveillance-broadcast ground sites 7 Area Control Centres, one each in: Vancouver – Surrey, BC Edmonton – Edmonton International Airport Winnipeg – Winnipeg-James Armstrong Richardson International Airport Toronto Centre – Toronto-Pearson International Airport Montreal Centre – Montreal-Trudeau International Airport Moncton – Riverview, New Brunswick Gander – Gander International Airport North Atlantic Oceanic control centre: Gander ControlNav Canada has three other facilities: National Operations Centre: Ottawa Technical Systems Centre: Ottawa The Nav Centre – 1950 Montreal Road in Cornwall, Ontario As a non-share capital corporation, Nav Canada has no shareholders.
The company is governed by a 15-member board of directors representing the four stakeholder groups that founded Nav Canada. The four stakeholders elect 10 members as follows: These 10 directors elect four independent directors, with no ties to the stakeholder groups; those 14 directors appoint the president and chief executive officer who becomes the 15th board member. This structure ensures that the interests of individual stakeholders do not predominate and no member group could exert undue influence over the remainder of the board. To further ensure that the interests of Nav Canada are served, these board members cannot be active employees or members of airlines, unions, or government; the company was formed on November 1, 1996 when the government sold the country's air navigation services from Transport Canada to the new not-for-profit private entity for CAD$1.5 billion. The company was formed in response to a number of issues with Transport Canada's operation of air traffic control and air navigation facilities.
While TC's safety record and operational staff were rated its infrastructure was old and in need of serious updating at a time of government restraint. This resulted in system delays for airlines and costs that were exceeding the airline ticket tax, a directed tax, supposed to fund the system; the climate of government wage freezes resulted in staff shortages of air traffic controllers that were hard to address within a government department. Having TC as the service provider, the regulator and inspector was a conflict of interest. Pressure from the airlines on the government mounted for a solution to the problem, hurting the air industry's bottom line. A number of solutions were considered, including forming a crown corporation, but rejected in favour of outright privatization, the new company being formed as a non-share-capital not-for-profit, run by a board of directors who were appointed and now elected; the company's revenue is predominately from service fees charged to aircraft operators which amount to about CAD$1.2B annually.
Nav Canada raises revenues from developing and selling technology and related services to other air navigation service providers around the world. It has some smaller sources of income, such as conducting maintenance work for other ANS providers and rentals from the Nav Centre in Cornwall, Ontario. To address the old infrastructure it purchased from the Canadian government the company has carried out projects such as implementing a wide area multilateration system, replacing 95 Instrument Landing System installations with new equipment, new control towers in Toronto and Calgary, modernizing the Vancouver Area Control Centre and building a new logistics centre Nav Canada felt the impact of the late-2000s recession in two ways: losses in its investments in third party sponsored asset-backed commercial paper and falling revenues due to reduced air traffic levels. In the summer of 2007 the company held $368 million in ABCP. On 12 January 2009 final Ontario Superior Court of Justice approval was granted to restructure the third party ABCP notes.
The company expects that the non-credit related fai
Simplex communication is a communication channel that sends information in one direction only. The International Telecommunication Union definition is a communications channel that operates in one direction at a time, but that may be reversible. A duplex communication channel requires two simplex channels operating in opposite directions. For example, in TV and radio broadcasting, information flows only from the transmitter site to multiple receivers. A pair of walkie-talkie two-way radios provide a simplex circuit in the ITU sense; the transmission medium can carry information in only one direction. The old Western Union company used the term simplex when describing the half-duplex and simplex capacity of their new transatlantic telegraph cable completed between Newfoundland and the Azores in 1928; the same definition for a simplex radio channel was used by the National Fire Protection Association in 2002
A computer network is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections between nodes; these data links are established over cable media such as wires or optic cables, or wireless media such as Wi-Fi. Network computer devices that originate and terminate the data are called network nodes. Nodes are identified by network addresses, can include hosts such as personal computers and servers, as well as networking hardware such as routers and switches. Two such devices can be said to be networked together when one device is able to exchange information with the other device, whether or not they have a direct connection to each other. In most cases, application-specific communications protocols are layered over other more general communications protocols; this formidable collection of information technology requires skilled network management to keep it all running reliably. Computer networks support an enormous number of applications and services such as access to the World Wide Web, digital video, digital audio, shared use of application and storage servers and fax machines, use of email and instant messaging applications as well as many others.
Computer networks differ in the transmission medium used to carry their signals, communications protocols to organize network traffic, the network's size, traffic control mechanism and organizational intent. The best-known computer network is the Internet; the chronology of significant computer-network developments includes: In the late 1950s, early networks of computers included the U. S. military radar system Semi-Automatic Ground Environment. In 1959, Anatolii Ivanovich Kitov proposed to the Central Committee of the Communist Party of the Soviet Union a detailed plan for the re-organisation of the control of the Soviet armed forces and of the Soviet economy on the basis of a network of computing centres, the OGAS. In 1960, the commercial airline reservation system semi-automatic business research environment went online with two connected mainframes. In 1963, J. C. R. Licklider sent a memorandum to office colleagues discussing the concept of the "Intergalactic Computer Network", a computer network intended to allow general communications among computer users.
In 1964, researchers at Dartmouth College developed the Dartmouth Time Sharing System for distributed users of large computer systems. The same year, at Massachusetts Institute of Technology, a research group supported by General Electric and Bell Labs used a computer to route and manage telephone connections. Throughout the 1960s, Paul Baran and Donald Davies independently developed the concept of packet switching to transfer information between computers over a network. Davies pioneered the implementation of the concept with the NPL network, a local area network at the National Physical Laboratory using a line speed of 768 kbit/s. In 1965, Western Electric introduced the first used telephone switch that implemented true computer control. In 1966, Thomas Marill and Lawrence G. Roberts published a paper on an experimental wide area network for computer time sharing. In 1969, the first four nodes of the ARPANET were connected using 50 kbit/s circuits between the University of California at Los Angeles, the Stanford Research Institute, the University of California at Santa Barbara, the University of Utah.
Leonard Kleinrock carried out theoretical work to model the performance of packet-switched networks, which underpinned the development of the ARPANET. His theoretical work on hierarchical routing in the late 1970s with student Farouk Kamoun remains critical to the operation of the Internet today. In 1972, commercial services using X.25 were deployed, used as an underlying infrastructure for expanding TCP/IP networks. In 1973, the French CYCLADES network was the first to make the hosts responsible for the reliable delivery of data, rather than this being a centralized service of the network itself. In 1973, Robert Metcalfe wrote a formal memo at Xerox PARC describing Ethernet, a networking system, based on the Aloha network, developed in the 1960s by Norman Abramson and colleagues at the University of Hawaii. In July 1976, Robert Metcalfe and David Boggs published their paper "Ethernet: Distributed Packet Switching for Local Computer Networks" and collaborated on several patents received in 1977 and 1978.
In 1979, Robert Metcalfe pursued making Ethernet an open standard. In 1976, John Murphy of Datapoint Corporation created ARCNET, a token-passing network first used to share storage devices. In 1995, the transmission speed capacity for Ethernet increased from 10 Mbit/s to 100 Mbit/s. By 1998, Ethernet supported transmission speeds of a Gigabit. Subsequently, higher speeds of up to 400 Gbit/s were added; the ability of Ethernet to scale is a contributing factor to its continued use. Computer networking may be considered a branch of electrical engineering, electronics engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of the related disciplines. A computer network facilitates interpersonal communications allowing users to communicate efficiently and via various means: email, instant messaging, online chat, video telephone calls, video conferencing. A network allows sharing of computing resources.
Users may access and use resources provided by devices on the network, such as printing a document on a shared network printer or use of a shared storage device. A network allows sharing of files, and
A semaphore telegraph is an early system of conveying information by means of visual signals, using towers with pivoting shutters known as blades or paddles. Information is encoded by the position of the mechanical elements; the most used system was invented in 1792 in France by Claude Chappe, was popular in the late eighteenth to early nineteenth centuries. Lines of relay towers with a semaphore rig at the top were built within line-of-sight of each other, at separations of 5–20 miles. Operators at each tower would watch the neighboring tower through a spyglass, when the semaphore arms began to move spelling out a message, they would pass the message on to the next tower; this system was much faster than post riders for conveying a message over long distances, had cheaper long-term operating costs, once constructed. Semaphore lines were a precursor of the electrical telegraph, which would replace them half a century and would be cheaper and more private; the line-of-sight distance between relay stations was limited by geography and weather, prevented the optical telegraph from crossing wide expanses of water, unless a convenient island could be used for a relay station.
Modern derivatives of the semaphore system include the heliograph. The word semaphore was coined in 1801 by the French inventor of the semaphore line itself, Claude Chappe, he composed it from the Greek elements σῆμα. Chappe coined the word tachygraph, meaning "fast writer". However, the French Army preferred to call Chappe's semaphore system the telegraph, meaning "far writer", coined by French statesman André François Miot de Mélito; the word semaphoric was first printed in English in 1808: "The newly constructed Semaphoric telegraphs", referring to the destruction of telegraphs in France. The word semaphore was first printed in English in 1816: "The improved Semaphore has been erected on the top of the Admiralty", referring to the installation of a simpler telegraph invented by Sir Home Popham. Semaphore telegraphs are called "optical telegraphs", "shutter telegraph chains", "Chappe telegraphs" or "Napoleonic semaphore". Optical telegraphy dates from ancient times, in the form of hydraulic telegraphs and smoke signals.
Modern design of semaphores was first foreseen by the British polymath Robert Hooke, who gave a vivid and comprehensive outline of visual telegraphy to the Royal Society in a 1684 submission in which he outlined many practical details. The system was never put into practice. One of the first experiments of optical signalling was carried out by the Anglo-Irish landowner and inventor, Sir Richard Lovell Edgeworth in 1767, he placed a bet with his friend, the horse racing gambler Lord March, that he could transmit knowledge of the outcome of the race in just one hour. Using a network of signalling sections erected on high ground, the signal would be observed from one station to the next by means of a telescope; the signal itself consisted of a large pointer that could be placed into eight possible positions in 45 degree increments. A series of two such signals gave a total 64 code elements and a third signal took it up to 512, he returned to his idea after hearing of Chappe's system. Credit for the first successful optical telegraph goes to the French engineer Claude Chappe and his brothers in 1792, who succeeded in covering France with a network of 556 stations stretching a total distance of 4,800 kilometres.
Le système Chappe was used for national communications until the 1850s. During 1790–1795, at the height of the French Revolution, France needed a swift and reliable communication system to thwart the war efforts of its enemies. France was surrounded by the forces of Britain, the Netherlands, Prussia and Spain, the cities of Marseille and Lyon were in revolt, the British Fleet held Toulon; the only advantage France held was the lack of cooperation between the allied forces due to their inadequate lines of communication. In the summer of 1790, the Chappe brothers set about devising a system of communication that would allow the central government to receive intelligence and to transmit orders in the shortest possible time. On 2 March 1791 at 11am, they sent the message “si vous réussissez, vous serez bientôt couverts de gloire” between Brulon and Parce, a distance of 16 kilometres; the first means used a combination of black and white panels, clocks and codebooks to send their message. The Chappes carried out experiments during the next two years, on two occasions their apparatus at Place de l'Étoile, Paris was destroyed by mobs who thought they were communicating with royalist forces.
However, in the summer of 1792 Claude was appointed Ingénieur-Télégraphiste and charged with establishing a line of stations between Paris and Lille, a distance of 230 kilometres. It was used to carry dispatches for the war between Austria. In 1794, it brought news of a French capture of Condé-sur-l'Escaut from the Austrians less than an hour after it occurred; the first symbol of a message to Lille would pass through 15 stations in only nine minutes. The speed of the line varied with the weather, but the line to Lille transferred 36 symbols, a complete message, in about 32 minutes. Another line of 50 stations was completed in 1798, covering 488 km betwe
In telecommunications a link is a communication channel that connects two or more devices. This link may be an actual physical link or it may be a logical link that uses one or more physical links or shares a physical link with other telecommunications links. A telecommunications link is one of several types of information transmission paths such as those provided by communication satellites, terrestrial radio communications infrastructure and computer networks to connect two or more points; the term link is used in computer networking to refer to the communications facilities that connect nodes of a network. When the link is a logical link the type of physical link should always be specified A point-to-point link is a dedicated link that connects two communication facilities. Broadcast links connect two or more nodes and support broadcast transmission, where one node can transmit so that all other nodes can receive the same transmission. Ethernet is an example. Known as a multidrop link, a multipoint link is a link that connects two or more nodes.
Known as general topology networks, these include ATM and Frame Relay links, as well as X.25 networks when used as links for a network layer protocol like IP. Unlike broadcast links, there is no mechanism to efficiently send a single message to all other nodes without copying and retransmitting the message. A point-to-multipoint link is a specific type of multipoint link which consists of a central connection endpoint, connected to multiple peripheral CEs. Any transmission of data that originates from the central CE is received by all of the peripheral CEs while any transmission of data that originates from any of the peripheral CEs is only received by the central CE. Links are referred to by terms which refer to the ownership and / or accessibility of the link. A private link is a link, either owned by a specific entity or a link, only accessible by a specific entity. A public link is a link that uses the public switched telephone network or other public utility or entity to provide the link and which may be accessible by anyone.
Pertaining to radiocommunication service, an uplink is the portion of a feeder link used for the transmission of signals from an earth station to a space radio station, space radio system or high altitude platform station. Pertaining to GSM and cellular networks, the radio uplink is the transmission path from the mobile station to a base station. Traffic and signalling flowing within the BSS and NSS may be identified as uplink and downlink. Pertaining to computer networks, an uplink is a connection from data communications equipment toward the network core; this is known as an upstream connection. Pertaining to radiocommunication service, a downlink is the portion of a feeder link used for the transmission of signals from a space radio station, space radio system or high altitude platform station to an earth station. In the context of satellite communications, a downlink is the link from a satellite to a ground station. Pertaining to cellular networks, the radio downlink is the transmission path from a cell site to the cell phone.
Traffic and signalling flowing within the base station subsystem and network switching subsystem may be identified as uplink and downlink. Pertaining to computer networks, a downlink is a connection from data communications equipment towards data terminal equipment; this is known as a downstream connection. A forward link is the link from a fixed location to a mobile user. If the link includes a communications relay satellite, the forward link will consist of both an uplink and a downlink; the reverse link is the link from a mobile user to a fixed base station. If the link includes a communications relay satellite, the reverse link will consist of both an uplink and a downlink which together constitute a half hop. Data transmission Telecommunications network This article incorporates public domain material from the General Services Administration document "Federal Standard 1037C"; this article incorporates public domain material from the United States Department of Defense document "Dictionary of Military and Associated Terms"
NATS Holdings National Air Traffic Services and referred to as NATS, is the main Air Navigation Service Provider in the United Kingdom. It inherited the traditions of UK air traffic control, the world's first air traffic control regime, it provides en-route air traffic control services to flights within the UK Flight Information Regions and the Shanwick Oceanic Control Area, provides air traffic control services to fourteen UK airports. The workforce of NATS is made up of Air traffic controllers, Air Traffic Control Engineers, Air Traffic Services Assistants and Science Technical Analytical and Research Staff. Administrative and Support staff make up the remainder of the 4,500 or so staff employed by NATS. NATS is split into two main service provision companies: NATS Services Ltd.. NERL is the sole provider of civilian en-route air traffic control over the UK and is regulated by the CAA who, for example, determine the charges NERL can make. NERL is funded by Eurocontrol route charges for the provision of air traffic services.
NSL competes for contracts to provide air traffic control at airports in the UK and overseas, as well as providing related services including engineering, information services and training. NATS' en-route business is operated under licence from the Civil Aviation Authority; the terms of the licence require NATS to be capable of meeting on a continuous basis any reasonable level of overall demand. They are charged with permitting access to airspace on the part of all users, whilst making the most efficient overall use of airspace; the organisation was set up as the National Air Traffic Control Services in 1962, bringing together responsibility for the UK's existing military and civil Air Traffic Control services. The organisation became National Air Traffic Services when responsibility for sponsoring the civil air traffic service component was transferred to the newly formed Civil Aviation Authority in 1972. Prior to this it had no legal existence – all contracts were with the CAA or MoD; until its establishment as a separate company, leadership of NATS alternated between civil and military, the latter a serving Air Marshal.
The first Controller was Sir Laurence Sinclair, exceptionally an Air Vice Marshal. NATS staff were drawn from, paid by, the CAA and the MoD; the London Air Traffic Control Centre at RAF West Drayton opened in 1966 and provided ATC services until it closed in 2007, with the move to Swanwick. Scottish air traffic control has been carried out from Atlantic House in Prestwick since 1978; this situation changed with the opening of the Prestwick Centre in 2010, to which all Operational Services were transferred from the old Atlantic House. The Prestwick Centre houses the Domestic and Oceanic Services and allows for state of the art technology to be introduced in future. In 1992 it was recognised that as a service provider, NATS should be operated at some distance from its regulator, the CAA. Although debated, it was decided. NATS was re-organised into a limited company on 1 April 1996 and became a wholly owned subsidiary of the CAA; the direct involvement of military officers in the management of NATS ended at this time, although the last military Controller had retired in 1991.
In 1998, a public-private partnership was proposed. This was written into the Transport Act 2000 and in 2001 51% of NATS was transferred to the private sector. However, due to the decline in air traffic following the September 11, 2001 attacks £130m of additional investment was required, £65m coming each from the UK government and BAA, who received 4% of the company in return; as a public-private partnership the UK government holds 49% and a golden share, with 42% held by the Airline Group, 5% by NATS staff, 4% by UK airport operator LHR Airports Limited. Martin Rolfe has been CEO of NATS since May 2015. Other Board members are listed here: http://www.nats.aero/about-us/board-executive/ In 2015 NATS handled 2,256,152 flights, an increase of 2.5% over 2014. Over the years NATS has grown from a UK focused business to a global business, with contracts in more than 30 countries, it offers aerodrome and consultancy solutions to worldwide customers which include airports, air traffic service providers and governments.
The company works through six Service Lines: There are two control locations in the UK operated by NERL: London Area Control Centre and London Terminal Control Centre at Swanwick in Hampshire control both upper level en-route traffic across England and Wales up to the Scottish border and low-level traffic around London and South East England, including aircraft making approaches to the main London airports. The Prestwick Centre, Ayrshire, is home to the Scottish Area Control Centre, which controls traffic over Scotland, Northern Ireland, up to FL285 over the northern half of England, the Prestwick Oceanic Area Control Centre which provides a procedural control service for traffic crossing the North Atlantic via the Shanwick Oceanic Control Area. Various radar stations are operated around one such being that on Great Dun Fell in Cumbria; the airports service line provides air traffic services at 14 UK airports: London Heathrow Airport Southampton Airport Aberdeen Airport London City Airport London Luton Airport London Stansted Airport Cardiff Airport Bristol Airport Farnborough Airfield Gibraltar Airport Manchester Airport Belfast International Airport Belfast City Airport Glasgow Airport Gatwick AirportNATS has won contracts to provide a part of the ai
A pager is a wireless telecommunications device that receives and displays alphanumeric or voice messages. One-way pagers can only receive messages, while response pagers and two-way pagers can acknowledge, reply to, originate messages using an internal transmitter. Pagers operate as part of a paging system which includes one or more fixed transmitters, as well as a number of pagers carried by mobile users; these systems can range from a restaurant system with a single low-power transmitter, to a nationwide system with thousands of high-power base stations. Pagers were developed in the 1950s and 1960s, became used by the 1980s. In the 21st century, the widespread availability of cellphones and smartphones has diminished the pager industry. Pagers continue to be used by some emergency services and public safety personnel, because modern pager systems' coverage overlap, combined with use of satellite communications, can make paging systems more reliable than terrestrial-based cellular networks in some cases, including during natural and man-made disasters.
This resilience has led public safety agencies to adopt pagers over cellular and other commercial services for critical messaging. The UK National Health Service is thought to use over 10% of remaining pagers in 2017, with an annual cost of £6.6 million. Matt Hancock announced in February 2019; the first telephone pager system was patented in 1949 by Alfred J. Gross. One of the first practical paging services was launched in 1950 for physicians in the New York City area. Physicians paid $12 per month for the service and carried a 200-gram pager that would receive phone messages within 40 kilometres of a single transmitter tower; the system was operated by Telanswerphone. In 1960, John Francis Mitchell combined elements of Motorola's walkie-talkie and automobile radio technologies to create the first transistorized pager, from that time, paging technology continued to advance, pager adoption among emergency personnel is still popular, as of July 2016. In 1962 the Bell System—the U. S. telephone monopoly colloquially known as "Ma Bell"—presented its Bellboy radio paging system at the Seattle World's Fair.
Bellboy was the first commercial system for personal paging. It marked one of the first consumer applications of the transistor, for which three Bell Labs inventors received a Nobel Prize in Physics in 1956. Solid-state circuitry enabled the Bellboy pager, about the size of a small TV remote device, to fit into a customer's pocket or purse, quite a feat at that time; the Bellboy was a terminal. When the person received an audible signal on the pager, he found a telephone and called the service centre, which informed him of the caller's message. Bell System Bellboy radio pagers each used three reed receiver relays, each relay tuned to one of 33 different frequencies, selectively ringing a particular customer when all three relays were activated at the same time—a precursor of DTMF; the ReFLEX protocol was developed in the mid-1990s. While Motorola announced the end of its new pager manufacturing in 2001, pagers remained in use in large hospital complexes. Another is a facility handling classified information, where various radio transmitter or data storage devices are excluded to ensure security.
First responders in rural areas with inadequate cellular coverage are issued pagers. The 2005 London bombings resulted in overload of TETRA systems by the emergency services, showed that pagers, with their absence of necessity to transmit an acknowledgement before showing the message, the related capability to operate on low signal levels, are not outclassed by their successors. Volunteer firefighters, EMS paramedics, rescue squad members carry pagers to alert them of emergency call outs for their department; these pagers receive a special tone from a fire department radio frequency. Restaurant pagers were in wide use in the 2000s. Customers were given a portable receiver that vibrates, flashes, or beeps when a table becomes free or when their meal is ready. Pagers have been popular with birdwatchers in Britain and Ireland since 1991, with companies Rare Bird Alert and Birdnet Information offering news of rare birds sent to pagers that they sell; the U. S. paging industry generated $2.1 billion in revenue in 2008, down from $6.2 billion in 2003.
In Canada, 161,500 Canadians paid $18.5 million for pager service in 2013. Telus, one of the three major mobile carriers, announced the end to its Canadian pager service as of March 31, 2015, but rivals Bell and PageNet intend to continue service. Many paging network operators now allow numeric and textual pages to be submitted to the paging networks via email; this is convenient for many users, due to the widespread adoption of email. This can result in pager messages being lost. Older forms of message submission using the Telelocator Alphanumeric Protocol involve modem connections directly to a paging network, are less subject to these delays. For this reason, older forms of message submission retain their usefulness for disseminating highly-important alerts to users such as emergency services personnel. Common paging protocols include TAP, FLEX, ReFLEX, POCSAG, GOLAY, ERMES and NTT. Past paging protocols include 5/6-tone. In the United States, pagers receive signals using the FLEX protocol in th