Credit card

A credit card is part of a system of payments named after the small plastic card issued to users of the system. It is a card entitling its holder to buy goods and services based on the holder's promise to pay for these goods and services.[1] The issuer of the card grants a line of credit to the consumer (or the user) from which the user can borrow money for payment to a merchant or as a cash advance to the user.
A credit card is different from a charge card, where a charge card requires the balance to be paid in full each month. In contrast, credit cards allow the consumers to 'revolve' their balance, at the cost of having interest charged. Most credit cards are issued by local banks or credit unions, and are the shape and size specified by the ISO/IEC 7810 standard as ID-1.

How credit card works

Credit cards are issued after an account has been approved by the credit provider, after which cardholders can use it to make purchases at merchants accepting that card.
When a purchase is made, the credit card user agrees to pay the card issuer. The cardholder indicates consent to pay by signing a receipt with a record of the card details and indicating the amount to be paid or by entering a personal identification number (PIN). Also, many merchants now accept verbal authorizations via telephone and electronic authorization using the Internet, known as a 'Card/Cardholder Not Present' (CNP) transaction.
Electronic verification systems allow merchants to verify that the card is valid and the credit card customer has sufficient credit to cover the purchase in a few seconds, allowing the verification to happen at time of purchase. The verification is performed using a credit card payment terminal or Point of Sale (POS) system with a communications link to the merchant's acquiring bank. Data from the card is obtained from a magnetic stripe or chip on the card; the latter system is in the United Kingdom and Ireland commonly known as Chip and PIN, but is more technically an EMV card.
Other variations of verification systems are used by eCommerce merchants to determine if the user's account is valid and able to accept the charge. These will typically involve the cardholder providing additional information, such as the security code printed on the back of the card, or the address of the cardholder.
Each month, the credit card user is sent a statement indicating the purchases undertaken with the card, any outstanding fees, and the total amount owed. After receiving the statement, the cardholder may dispute any charges that he or she thinks are incorrect (see Fair Credit Billing Act for details of the US regulations). Otherwise, the cardholder must pay a defined minimum proportion of the bill by a due date, or may choose to pay a higher amount up to the entire amount owed. The credit issuer charges interest on the amount owed if the balance is not paid in full (typically at a much higher rate than most other forms of debt). Some financial institutions can arrange for automatic payments to be deducted from the user's bank accounts, thus avoiding late payment altogether as long as the cardholder has sufficient funds.

Elevators

An elevator or lift (in British English) is a vertical transport vehicle that efficiently moves people or goods between floors of a building. They are generally powered by electric motors that either drive traction cables and counterweight systems, or pump hydraulic fluid to raise a cylindrical piston.
Languages other than English may have loanwords based on either elevator (e.g., Japanese) or lift (e.g., Cantonese).
Because of wheelchair access laws, elevators are often a legal requirement in new multi-story buildings, especially where wheelchair ramps would be impractical.

Design

Lifts began as simple rope or chain hoists. A lift is essentially a platform that is either pulled or pushed up by a mechanical means. A modern day lift consists of a cab (also called a "cage" or "car") mounted on a platform within an enclosed space called a shaft or sometimes a "hoistway". In the past, lift drive mechanisms were powered by steam and water hydraulic pistons. In a "traction" lift, cars are pulled up by means of rolling steel ropes over a deeply grooved pulley, commonly called a sheave in the industry. The weight of the car is balanced with a counterweight. Sometimes two lifts always move synchronously in opposite directions, and they are each other's counterweight.
The friction between the ropes and the pulley furnishes the traction which gives this type of lift its name.
For more details on this topic, see #Hydraulic elevators.
Hydraulic lift use the principles of hydraulics (in the sense of hydraulic power) to pressurize an above ground or in-ground piston to raise and lower the car. Roped Hydraulics use a combination of both ropes and hydraulic power to raise and lower cars. Recent innovations include permanent earth magnet motors, machine room-less rail mounted gearless machines, and microprocessor controls.
Which technology is used in new installations depends on a variety of factors. Hydraulic lifts are cheaper, but installing cylinders greater than a certain length becomes impractical for very high lift hoistways. For buildings of much over seven stories, traction lift must be employed instead. Hydraulic lifts are usually slower than traction lifts.
Lifts are a candidate for mass customization. There are economies to be made from mass production of the components, but each building comes with its own requirements like different number of floors, dimensions of the well and usage patterns.

Elevator doors
Elevator doors protect building tenants from falling into the shaft. The most common configuration is to have two panels that meet in the middle, and slide open laterally. In a cascading configuration (potentially allowing wider entryways within limited space), the doors run on independent tracks so that while open, they are tucked behind one another, and while closed, they form cascading layers on one side.

Machine Room-less
All elevators, whether traction or hydraulic, require a machine room to store large electric motors (or hydraulic pumps) and a controller cabinet. This room is located above the hoistway (or below, for hydraulic elevators) and may contain machinery for a single or a group of elevators. Modern day traction motors boasting gearless and permanent magnet drive more compact and efficient; electronic microprocessors have replaced the mechanical relays. As a result, traction elevators can be built without a dedicated room above the shaft, saving valuable space in building planning.
The new lift design presents a departure from the traditional, looped over-the-top traction rope routing of traction elevators. The ends of the cables are fixed to the supporting structure, and the length of the cable are connected to the car and counterweight by means of a force-multiplying, energy saving compound pulley system. Machine Room-less elevators have become a welcome alternative to the older hydraulic elevator for low to medium rise buildings.

Card door

A door card (in British English) or a door panel (in American English) in an insert on the door of a car that covers the door's internal components. The door card will usually match the rest of the interior and is usually made of plastic in modern cars though it may be covered in vinyl or leather.

security camera

Closed-circuit television (CCTV) is the use of video cameras to transmit a signal to a specific place, on a limited set of monitors.
It differs from broadcast television in that the signal is not openly transmitted, though it may employ point to point wireless links. CCTV is often used for surveillance in areas that may need monitoring such as banks, casinos, airports, military installations, and convenience stores.
In industrial plants, CCTV equipment may be used to observe parts of a process from a central control room; when, for example, the environment is not suitable for humans. CCTV systems may operate continuously or only as required to monitor a particular event. A more advanced form of CCTV, utilizing Digital Video Recorders (DVRs), provides recording for possibly many years, with a variety of quality and performance options and extra features (such as motion-detection and email alerts).
Surveillance of the public using CCTV is particularly common in the UK, where there are reportedly more cameras per person than in any other country in the world.[1] There and elsewhere, its increasing use has triggered a debate about security versus privacy.

History

The first CCTV system was installed by Siemens AG at Test Stand VII in Peenemünde, Germany in 1942, for observing the launch of V-2 rockets.[2] The noted German engineer Walter Bruch was responsible for the design and installation of the system.
CCTV recording systems are still often used at modern launch sites to record the flight of the rockets, in order to find the possible causes of malfunctions,[3][4] while larger rockets are often fitted with CCTV allowing pictures of stage separation to be transmitted back to earth by radio link.[5]
In September 1968, Olean, New York was the first city in the United States to install video cameras along its main business street in an effort to fight crime.[citation needed] The use of closed-circuit TV cameras piping images into the Olean Police Department propelled Olean to the forefront of crime-fighting technology.
The use of CCTV later on became very common in banks and stores to discourage theft, by recording evidence of criminal activity. Their use further popularised the concept. The first place to use CCTV in the United Kingdom was King's Lynn, Norfolk.[6]
In recent decades, especially with general crime fears growing in the 1990s and 2000s, public space use of surveillance cameras has taken off, especially in some countries such as the United Kingdom.

Uses

Crime prevention and prevalence in the UK
Outside government special facilities, CCTV was developed initially as a means of increasing security in banks. Experiments in the UK during the 1970s and 1980s (including outdoor CCTV in Bournemouth in 1985), led to several larger trial programs later that decade.[6]
These were deemed successful in the government report "CCTV: Looking Out For You", issued by the Home Office in 1994, and paved the way for a massive increase in the number of CCTV systems installed. Today, systems cover most town and city centres, and many stations, car-parks and estates.
The exact number of CCTV cameras in the UK is not known but a 2002 working paper by Michael McCahill and Clive Norris of UrbanEye,[7] based on a small sample in Putney High Street, estimated the number of surveillance cameras in private premises in London is around 500,000 and the total number of cameras in the UK is around 4,200,000.
According to their estimate the UK has one camera for every 14 people, although it has been acknowledged that the methodology behind this figure is somewhat dubious.[8] The CCTV User Group estimate that there are around 1.5 million CCTV cameras in city centres, stations, airports, major retail areas and so forth. This figure does not include the smaller surveillance systems such as those that may be found in local corner shops. [9]
However, there is little evidence that CCTV deters crime.[10] According to a Liberal Democrat analysis, in London "Police are no more likely to catch offenders in areas with hundreds of cameras than in those with hardly any."[11] A 2008 Report by UK Police Chiefs concluded that only 3% of crimes were solved by CCTV. [12]
Cameras have also been installed in taxis in the hope of deterring violence against drivers,[13][14] and in mobile police surveillance vans.[15] In some cases CCTV cameras have become a target of attacks themselves.[16] Middlesbrough council have recently installed "Talking CCTV" cameras in their busy town-centre.[17] It is a system pioneered in Wiltshire, which allows CCTV operators to communicate directly with the offenders they spot.[18]

The two-year-old James Bulger being led away by his killers, recorded on shopping centre CCTV.
The most measurable effect of CCTV is not on crime prevention, but on a small number of high media-profile case of detection. The investigation or prosecution of several notable murder cases have been aided by the use of CCTV evidence; such as the apprehension of David Copeland, the Soho nail bomber. The use of CCTV to track the movements of missing children is now routine.[citation needed]
After the 7 July 2005 London bombings, CCTV footage was used to identify the bombers.
On 22 July 2005, Jean Charles de Menezes was shot dead by police at Stockwell tube station. CCTV footage debunked claims made by the Metropolitan Police in defence of the shooting of an innocent man.[19]
Because of the bombing attempts the previous day, some of the tapes had been supposedly removed from CCTV cameras for study, and they were not functional.[20] An ongoing change to DVR based technology may in future stop similar problems occurring.[21]
The UK cameras were deployed and are maintained by NEP - Roll to Record, a division of NEP Broadcasting.[22]
In the UK, CCTV is also used to target anti-social behaviour. In many areas, Local Authority CCTV works with the police to combat, for example, drink-related anti-social behaviour in town/city centres or youth-related anti social behaviour in housing estates.

Bar code

A barcode (also bar code) is an optical machine-readable representation of data. Originally, bar codes represented data in the widths (lines) and the spacings of parallel lines, and may be referred to as linear or 1D (1 dimensional) barcodes or symbologies. They also come in patterns of squares, dots, hexagons and other geometric patterns within images termed 2D (2 dimensional) matrix codes or symbologies. Although 2D systems use symbols other than bars, they are generally referred to as barcodes as well.
The first use of barcodes was to label railroad cars, but they were not commercially successful until they were used to automate supermarket checkout systems, a task in which they have become almost universal. Their use has spread to many other roles as well, tasks that are generically referred to as Auto ID Data Capture (AIDC). Systems such as attempting to make inroads in the AIDC market, but the simplicity, universality and low cost of barcodes has limited the role of these other systems. It costs about US$0.005 to implement a barcode compared to passive RFID which still costs about US$0.07 to US$0.30 per tag.[1]
Barcodes can be read by optical scanners called barcode readers, or scanned from an image by special software. In Japan, most mobile phones have built-in scanning software for 2D codes, and similar software is becoming available on smartphone platforms.

History

In 1932 business student Wallace Flint of the Harvard University Graduate School of Business Administration wrote a thesis promoting an "automated grocery store" using punch cards, which customers would hand to a clerk, who would load them into a reader, causing flow racks to deliver the desired products, after which an itemized bill would automatically be produced.[2] In spite of its promise, punch card systems were expensive, and the country was in the midst of the Great Depression, and the idea was never implemented.
In 1948 Bernard Silver (1924-62), a graduate student at Drexel Institute of Technology in Philadelphia, overheard the president of a local food chain asking one of the deans to research a system to automatically read product information during checkout. Silver told his friends Norman Joseph Woodland (1921-) and Jordin Johanson about the request, and the three started working on a variety of systems. Their first working system used ultraviolet ink, but this proved to fade and was fairly expensive.[2]
Convinced that the system was workable with further development, Woodland quit his position at Drexel, moved into his father's apartment in Florida, and continued working on the system. His next inspiration came from Morse code, and he formed his first barcode from sand on the beach when "I just extended the dots and dashes downwards and made narrow lines and wide lines out of them."[2] To read them, he adapted technology from optical soundtracks in movies, using a 500-watt light bulb shining through the paper onto an RCA935 photomultiplier tube (from a movie projector) on the far side. He later decided that the system would work better if it were printed as a circle instead of a line, allowing it to be scanned in any direction.
On October 20, 1949, they filed a patent application for "Classifying Apparatus and Method", in which they described both the linear and bullseye printing patterns, as well as the mechanical and electronic systems needed to read the code. The patent was issued on October 7, 1952 as US Patent 2,612,994. In 1951 Woodland and Johanson moved to IBM and continually tried to interest them in developing the system. They eventually commissioned a report on the idea, which concluded that it was both feasible and interesting, but that processing the resulting information would require equipment that was some time off in the future.
In 1952 Philco purchased their patent, and then sold it to RCA the same year. In 1962 Silver died in an automobile accident.

Collins at Sylvania

During his undergraduate degree, David Collins worked at the Pennsylvania Railroad and became aware of the need to automatically identify train cars. Immediately after receiving his master's degree from MIT in 1959, he started work at Sylvania and began addressing the problem. He developed a system using blue and yellow reflective stripes attached to the side of the cars, encoding a six-digit company identifier and a four-digit car number. Light reflected off the stripes was fed into one of two photomultipliers, filtered for blue or yellow.
The Boston and Maine Railroad tested the system on their gravel cars in 1961. The tests continued until 1967, when the Association of American Railroads (AAR) selected it as a standard across the entire North American fleet. The installations began on October 10, 1967. However, the economic downturn and rash of bankruptcies in the industry in the early 1970s greatly slowed the rollout, and it wasn't until 1974 that 95% of the fleet was labeled. To add to its woes, the system was found to be easily fooled by dirt in certain applications, and the accuracy was greatly affected. The AAR abandoned the system in the late 1970s, and it was not until the mid-1980s that they introduced a similar system, this time based on radio tags.
The railway project had proven to be a bust, but a toll bridge in New Jersey requested that a similar system be developed so that it could quickly scan for cars that had paid for a monthly pass. Then the U.S. Post Office requested the development of a system to keep track of the trucks entering and leaving their facilities. These applications required special retroreflective labels. Finally, Kal Kan asked the Sylvania team to develop a simpler (and cheaper) version which they could put on cases of pet food for inventory control. This, in turn, led to the grocery industry's interest.

Computer identics

In 1967, with the railway system maturing, Collins went to management looking for funding for a project to develop a black and white version of the code for other industries. They declined, saying that the railway project was large enough and they saw no need to branch out so quickly.
Collins then quit Sylvania and formed Computer Identics. Computer Identics started working with helium-neon lasers in place of light bulbs, scanning with a mirror to locate the barcode anywhere up to several feet in front of the scanner. This made the entire process much simpler and more reliable, as well as allowing it to deal with ripped codes by reading the intact portions.
Computer Identics installed their first two systems in early 1969, one at a General Motors factory in Pontiac, Michigan, and another at a distribution center at the General Trading Company in Carlstadt, New Jersey[citation needed]. The General Motors system was used to identify car axles in inventory among the 18 models produced at the factory.

UPC

In 1966 the National Association of Food Chains (NAFC) held a meeting where they discussed the idea of using automated checkout systems. RCA, having purchased rights to the original Woodland patent, had attended the meeting and set up an internal project to develop a system based on the bullseye code. The Kroger grocery chain volunteered to test it.
In mid-1970, the NAFC established the U.S. Supermarket Ad Hoc Committee on a Uniform Grocery Product Code, which set guidelines for barcode development and created a symbol selection subcommittee to help standardize the approach. In cooperation with consulting firm McKinsey & Co., they developed a standardized 11-digit code to identify any product. The committee then sent out a contract tender to develop a system to print and read the code. The request went to Singer, National Cash Register (NCR), Litton Industries, RCA, Pitney-Bowes, IBM and many others.[3] A wide variety of barcode approaches were studied, including linear codes, RCA's bullseye concentric circle code, systems with starburst patterns, and even odder varieties.
In the spring of 1971 RCA demonstrated their bullseye code at another industry meeting, and IBM executives at the meeting noticed the crowds at the RCA booth, immediately setting out to develop their own system. IBM marketing specialist Alec Jablonover remembered that the company still employed the system's inventor Woodland, and he was set up in new facilities in North Carolina to lead the development.
In July 1972 RCA began an eighteen-month test of their system in a Kroger store in Cincinnati. Barcodes were printed on small pieces of adhesive paper, and attached by hand by store employees when they were adding price tags. The code proved to have a serious problem. During printing, presses sometimes smear ink in the direction the paper is running, rendering the code unreadable in most orientations. A linear code, like the one being developed by Woodland at IBM, however, was printed in the direction of the stripes, so extra ink simply makes the code "taller" while remaining readable, and on April 3, 1973 the IBM UPC code was selected by NAFC as their standard.
NCR installed a testbed system at Marsh's Supermarket in Troy, Ohio, near the factory that was producing the equipment. On June 26, 1974, Clyde Dawson pulled a 10-pack of Wrigley's Juicy Fruit gum out of his basket and it was scanned by Sharon Buchanan at 8:01 am. The pack of gum and the receipt are now on display in the Smithsonian Institution.
Economic studies conducted for the grocery industry committee projected over $40 million in savings to the industry from scanning by the mid-1970s. Those numbers were not achieved in that time frame and there were those who predicted the demise of barcode scanning. The usefulness of the barcode required the adoption of expensive scanners by a critical mass of retailers while manufacturers simultaneously adopted barcode labels. Neither wanted to move first and results weren't promising for the first couple of years, with Business Week proclaiming "The Supermarket Scanner That Failed."[4]
However, IBM already had solved that problem. For years IBM had worked to computerize the grocery industry. RCA and Krogers asked IBM to get involved in the effort to scan products in checkout lines. IBM had employees study various aspects of grocery industry functions. In 1971 they assembled a team for in an intensive planning session, day after day, 12 to 18 hours a day, to hash out how the whole system might operate and to schedule a rollout plan. By 1973 they were meeting with grocery manufacturers to introduce them to the symbol that would need to be printed on all of their products for the rollout of the system that established the Barcode as the universal system it now is.[5]
IBM had designed five versions of the UPC symbology for future industry requirements — UPC A, B, C, D, and E [6] The U.P.C. made its first commercial appearance at the Marsh Supermarket in Troy, Ohio in June 1974.[4]

Barcode reader

A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes. Like a flatbed scanner, it consists of a light source, a lens and a light sensor translating optical impulses into electrical ones. Additionally, nearly all barcode readers contain decoder circuitry analyzing the barcode's image data provided by the sensor and sending the barcode's content to the scanner's output port.

Types of barcode readers

Methods
Scanning methods are distinguished by the amount of operator manipulation required:
Pen or wand-type readers: requires the operator to swipe the pen over the code.
Semi-automatic handheld readers: The operator need not swipe, but must at least position the reader near the label
Fix-mount readers for automatic reading: The reading is performed laterally passing the label over the reader. No operator is required, but the position of the code target must coincide with the imaging capability of the reader.
Reader gates for automatic scanning: The position of the code must be just under the gate for short time, enabling the scanner sweep to capture the code target successfully.

Types of technology
The reader types can be distinguished as follows:
Pen type readers
Pen type readers consist of a light source and a photodiode that are placed next to each other in the tip of a pen or wand.[1] To read a bar code, the tip of the pen moves across the bars in a steady motion. The photodiode measures the intensity of the light reflected back from the light source and generates a waveform that is used to measure the widths of the bars and spaces in the bar code. Dark bars in the bar code absorb light and white spaces reflect light so that the voltage waveform generated by the photo diode is a representation of the bar and space pattern in the bar code. This waveform is decoded by the scanner in a manner similar to the way Morse code dots and dashes are decoded.
Laser scanners
Laser scanners work the same way as pen type readers except that they use a laser beam as the light source and typically employ either a reciprocating mirror or a rotating prism to scan the laser beam back and forth across the bar code.[1] As with the pen type reader, a photodiode is used to measure the intensity of the light reflected back from the bar code. In both pen readers and laser scanners, the light emitted by the reader is tuned to a specific frequency and the photodiode is designed to detect only this modulated light of the same frequency.
CCD Readers
CCD readers (also referred to as LED scanner) use an array of hundreds of tiny light sensors lined up in a row in the head of the reader.[1] Each sensor measures the intensity of the light immediately in front of it. Each individual light sensor in the CCD reader is extremely small and because there are hundreds of sensors lined up in a row, a voltage pattern identical to the pattern in a bar code is generated in the reader by sequentially measuring the voltages across each sensor in the row. The important difference between a CCD reader and a pen or laser scanner is that the CCD reader is measuring emitted ambient light from the bar code whereas pen or laser scanners are measuring reflected light of a specific frequency originating from the scanner itself.
Camera-Based Readers
2D imaging scanners are the fourth and newest type of bar code reader currently available. They use a small video camera to capture an image of a bar code. The reader then uses sophisticated digital image processing techniques to decode the bar code. Video cameras use the same CCD technology as in a CCD bar code reader except that instead of having a single row of sensors, a video camera has hundreds of rows of sensors arranged in a two dimensional array so that they can generate an image.
There are a number of open source libraries for barcode reading from images. These include the ZXing project, which reads one- and two-dimensional barcodes using Android and JavaME, the JJIL project, which includes code for reading EAN-13 barcodes from cellphone cameras using J2ME, and Zebra (Changed name to ZBAR?), which reads various one-dimensional barcodes in C. Even web site integration, either by image uploads (e.g. Folke Ashberg: EAN-13 Image-Scanning and code creation tools) or by use of plugins (e.g. the Barcodepedia uses a flash application and some web cam for querying a database), have been realized options for resolving the given tasks.
Omni-Directional Barcode Scanners
Omni-directional scanning uses "series of straight or curved scanning lines of varying directions in the form of a starburst, a lissajous pattern, or other multiangle arrangement are projected at the symbol and one or more of them will be able to cross all of the symbol's bars and spaces, no matter what the orientation."[2]
Omni-directional scanners almost all use a laser. Unlike the simpler single-line laser scanners, they produce a pattern of beams in varying orientations allowing them to read barcodes presented to it at different angles. Most of them use a single rotating polygonal mirror and an arrangement of several fixed mirrors to generate their complex scan patterns.
Omni-directional scanners are most familiar through the horizontal scanners in supermarkets, where packages are slid across a glass or sapphire window. There are a range of different omni-directional units available which can be used for differing scanning applications, ranging from retail type applications with the barcodes read only a few centimetres away from the scanner to industrial conveyor scanning where the unit can be a couple of metres away or more from the code.
Omni-directional scanners are also better at reading poorly printed, wrinkled, or even torn barcodes.

Telegraph

Telegraphy is the long-distance transmission of written messages without physical transport of letters. It is a compound term formed from the Greek words tele (τηλε) = far and graphein (γραφειν) = write. Radiotelegraphy or wireless telegraphy transmits messages using radio. Telegraphy includes recent forms of data transmission such as fax, email, and computer networks in general.

Terminology

A telegraph is a device for transmitting and receiving messages over long distances, i.e., for telegraphy. The word telegraph alone now generally refers to an electrical telegraph. Wireless telegraphy is also known as 'CW', for Continuous Wave (a carrier modulated by on-off keying), as opposed to the earlier radio technique of using a spark gap.[citation needed]
A telegraph message sent by an electrical telegraph operator (or telegrapher) using Morse code, or a printing telegraph operator using plain text was known as a telegram or cablegram, often shortened to a cable or a wire message. Later, a telegram sent by a Telex network, a switched network of teleprinters similar to a telephone network, was known as a telex message.
Before long distance telephone services were readily available or affordable, telegram services were very popular and the only way to convey information speedily over very long distances. Telegrams were often used to confirm business dealings and were commonly used to create binding legal documents for business dealings.[1]
A wire picture or wire photo was a newspaper picture that was sent from a remote location by a facsimile telegraph. The teleostereograph machine, a forerunner to the modern electronic fax, was developed by AT&T's Bell Labs in the 1920s; however the first commercial use of image facsimile telegraph devices date back to the 1800s.

Optical telegraph

The first telegraphs came in the form of optical telegraphs, including the use of smoke signals, beacons or reflected light, which have existed since ancient times. A semaphore network invented by Claude Chappe operated in France from 1792 through 1846.[2] It helped Napoleon enough to be widely imitated in Europe and the U.S. The Prussian system was put into effect in the 1830s. The last commercial semaphore link ceased operation in Sweden in 1880.
Semaphores were able to convey information more precisely than smoke signals and beacons, and consumed no fuel. Messages could be sent at much greater speed than post riders and could serve entire regions. However, like beacons, smoke and reflected light signals they were highly dependent on good weather and daylight to work (practical electrical lighting was not available until about 1880). They required operators and towers every 30 km (20 mi), and could only accommodate about two words per minute. This was useful to governments, but too expensive for most commercial uses other than commodity price information. Electric telegraphs were to reduce the cost of sending a message thirtyfold compared to semaphores, and could be utilized non-stop, 24 hours per day, independent of the weather or daylight.
Elevated locations where optical telegraphs were placed for maximum visibility were renamed to Telegraph Hill, such as Telegraph Hill, San Francisco, and Telegraph Hill in the PNC Bank Arts Center in New Jersey.

Television(TV)

Television (TV) is a widely used telecommunication medium for transmitting and receiving moving images, either monochromatic ("black and white") or color, usually accompanied by sound. "Television" may also refer specifically to a television set, television programming or television transmission. The word is derived from mixed Latin and Greek roots, meaning "far sight": Greek tele (τῆλε), far, and Latin visio, sight (from video, vis- to see, or to view in the first person).
Commercially available since the late 1930s, the television set has become a common communications receiver in homes, businesses and institutions, particularly as a source of entertainment and news. Since the 1970s the availability of video cassettes, laserdiscs, DVDs and now Blu-ray discs, have resulted in the television set frequently being used for viewing recorded as well as broadcast material.
Although other forms such as closed-circuit television are in use, the most common usage of the medium is for broadcast television, which was modeled on the existing radio broadcasting systems developed in the 1920s, and uses high-powered radio-frequency transmitters to broadcast the television signal to individual TV receivers.
Broadcast TV is typically disseminated via radio transmissions on designated channels in the 54-890 megahertz frequency band[1]. Signals are now often transmitted with stereo and/or surround sound in many countries. Until the 2000s broadcast TV programs were generally recorded and transmitted as an analog signal, but in recent years public and commercial broadcasters have been progressively introducing digital television broadcasting technology.
A standard television set comprises multiple internal electronic circuits, including those for receiving and decoding broadcast signals. A visual display device which lacks a tuner is properly called a monitor, rather than a television. A television system may use different technical standards such as digital television (DTV) and high-definition television (HDTV). Television systems are also used for surveillance, industrial process control, and guiding of weapons, in places where direct observation is difficult or dangerous.
Amateur television (HAM TV or ATV) is also used for experimentation, pleasure and public service events by amateur radio operators. HAM TV stations were on the air in many cities before commercial TV stations came on the air

History

In its early stages of development, television employed a combination of optical, mechanical and electronic technologies to capture, transmit and display a visual image. By the late 1920s, however, those employing only optical and electronic technologies were being explored. All modern television systems rely on the latter, although the knowledge gained from the work on mechanical-dependent systems was crucial in the development of fully electronic television.
The first time images were transmitted electrically were via early mechanical fax machines, including the pantelegraph, developed in the late 1800s. The concept of electrically-powered transmission of television images in motion, was first sketched in 1878 as the telephonoscope, shortly after the invention of the telephone. At the time, it was imagined by early science fiction authors, that someday that light could be transmitted over wires, as sounds were.[citation needed]
The idea of using scanning to transmit images was put to actual practical use in 1881 in the pantelegraph, through the use of a pendulum-based scanning mechanism. From this period forward, scanning in one form or another, has been used in nearly every image transmission technology to date, including television. This is the concept of "rasterization", the process of converting a visual image into a stream of electrical pulses.[citation needed]
In 1884 Paul Gottlieb Nipkow, a 20-year old university student in Germany, patented the first electromechanical television system which employed a scanning disk, a spinning disk with a series of holes spiraling toward the center, for rasterization. The holes were spaced at equal angular intervals such that in a single rotation the disk would allow light to pass through each hole and onto a light-sensitive selenium sensor which produced the electrical pulses. As an image was focused on the rotating disk, each hole captured a horizontal "slice" of the whole image, in a scanning fashion.[citation needed]
Nipkow's design would not be practical until advances in amplifier tube technology became available in 1907. Even then the device was only useful for transmitting still "halftone" images - represented by equally spaced dots of varying size - over telegraph or telephone lines. Later designs would use a rotating mirror-drum scanner to capture the image and a cathode ray tube (CRT) as a display device, but moving images were still not possible, due to the poor sensitivity of the selenium sensors.[citation needed]
Scottish inventor John Logie Baird demonstrated the transmission of moving silhouette images in London in 1925, and of moving, monochromatic images in 1926. Baird's scanning disk produced an image of 30 lines resolution, just enough to discern a human face, from a double spiral of lenses.[citation needed]. Remarkably, in 1927 Baird also invented the world's first video recording system, "Phonovision" -- by modulating the output signal of his TV camera down to the audio range he was able to capture the signal on a 10-inch wax audio disc using conventional audio recording technology. A handful of Baird's 'Phonovision' recordings survive and these were finally decoded and rendered into viewable images in the 1990s using modern digital signal-processing technology[4].
In 1926, Hungarian engineer Kálmán Tihanyi designed a television system utilizing fully electronic scanning and display elements, and employing the principle of "charge storage" within the scanning (or "camera") tube.[5][6][7][8]
By 1927, Russian inventor Léon Theremin developed a mirror drum-based television system which used interlacing to achieve an image resolution of 100 lines.[citation needed]
Also in 1927, Herbert E. Ives of Bell Labs transmitted moving images from a 50-aperture disk producing 16 frames per minute over a cable from Washington, DC to New York City, and via radio from Whippany, New Jersey. Ives used viewing screens as large as 24 by 30 inches (60 by 75 centimeters). His subjects included Secretary of Commerce Herbert Hoover.[citation needed]
In 1927, Philo Farnsworth made the world's first working television system with electronic scanning of both the pickup and display devices,[9] which he first demonstrated to news media on 1 September 1928, televising a motion picture film.[citation needed]
The first practical use of television was in Germany. Regular television broadcasts began in Germany in 1929 and in 1936 the Olympic Games in Berlin were broadcast to television stations in Berlin and Leipzig where the public could view the games live.[10]
In 1936, Kálmán Tihanyi described the principle of plasma television, the first flat panel

Radio

Radio is the transmission of signals by modulation of electromagnetic waves with frequencies below those of visible light.[1] Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space. Information is carried by systematically changing (modulating) some property of the radiated waves, such as amplitude, frequency, or phase. When radio waves pass an electrical conductor, the oscillating fields induce an alternating current in the conductor. This can be detected and transformed into sound or other signals that carry information.

Etymology

Originally, radio or radiotelegraphy was called "wireless telegraphy", which was shortened to "wireless" by the British. The prefix radio- in the sense of wireless transmission, was first recorded in the word radioconductor, coined by the French physicist Édouard Branly in 1897 and based on the verb to radiate (in Latin "radius" means "spoke of a wheel, beam of light, ray"). "Radio" as a noun is said to have been coined by the advertising expert Waldo Warren (White 1944). This word also appears in a 1907 article by Lee De Forest, was adopted by the United States Navy in 1912 and became common by the time of the first commercial broadcasts in the United States in the 1920s. (The noun "broadcasting" itself came from an agricultural term, meaning "scattering seeds widely".) The term was then adopted by other languages in Europe and Asia. British Commonwealth countries continued to mainly use the term "wireless" until the mid-20th century, though the magazine of the BBC in the UK has been called Radio Times ever since it was first published in the early 1920s.
In recent years the term "wireless" has gained renewed popularity through the rapid growth of short-range computer networking, e.g., Wireless Local Area Network (WLAN), WiFi, and Bluetooth, as well as mobile telephony, e.g., GSM and UMTS. Today, the term "radio" often refers to the actual transceiver device or chip, whereas "wireless" refers to the system and/or method used for radio communication, hence one talks about radio transceivers and Radio Frequency Identification (RFID), but about wireless devices and wireless sensor networks.

Proceses

Radio systems used for communications will have the following elements. With more than 100 years of development, each process is implemented by a wide range of methods, specialized for different communications purposes.
Each system contains a transmitter. This consists of a source of electrical energy, producing alternating current of a desired frequency of oscillation. The transmitter contains a system to modulate (change) some property of the energy produced to impress a signal on it. This modulation might be as simple as turning the energy on and off, or altering more subtle properties such as amplitude, frequency, phase, or combinations of these properties. The transmitter sends the modulated electrical energy to an antenna; this structure converts the rapidly-changing alternating current into an electromagnetic wave that can move through free space.
Electromagnetic waves travel through space either directly, or have their path altered by reflection, refraction or diffraction. The intensity of the waves diminishes due to geometric dispersion (the inverse-square law); some energy may also be absorbed by the intervening medium in some cases. Noise will generally alter the desired signal; this electromagnetic interference comes from natural sources, as well as from artificial sources such as other transmitters and accidental radiators. Noise is also produced at every step due to the inherent properties of the devices used. If the magnitude of the noise is large enough, the desired signal will no longer be discernible; this is the fundamental limit to the range of radio communications.
The electromagnetic wave is intercepted by a receiving antenna; this structure captures some of the energy of the wave and returns it to the form of oscillating electrical currents. At the receiver, these currents are demodulated, which is conversion to a usable signal form by a detector sub-system. The receiver is "tuned" to respond preferentially to the desired signals, and reject undesired signals.
Early radio systems relied entirely on the energy collected by an antenna to produce signals for the operator. Radio became more useful after the invention of electronic devices such as the vacuum tube and later the transistor, which made it possible to amplify weak signals. Today radio systems are used for applications from walkie-talkie children's toys to the control of space vehicles, as well as for broadcasting, and many other applications.

Tape recorder

A tape recorder, tape deck, reel-to-reel tape deck, cassette deck or tape machine is an audio storage device that records and plays back sound using magnetic tape, either wound on a reel or in a cassette, for storage. It records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal.

History

Early tape recorders were created by replacing the steel wire of a wire recorder with a thin steel tape. The first of these modified wire recorders was the Blattnerphone, created in 1929 or 1930 by the Ludwig Blattner Picture Corporation. The first practical tape recorder was called K1 and demonstrated in Germany in 1935. Friedrich Matthias of IG Farben/BASF developed the recording tape, including the oxide, the binder, and the backing material. Development of magnetic tape recorders in the late 1940s and early 1950s is associated with the Brush Development Company and its licensee, Ampex; the equally important development of magnetic tape media itself was led by Minnesota Mining and Manufacturing Company (now known as 3M).

History:

Electrical
Electric current flowing in the coils of the tape head creates a fluctuating magnetic field. This causes the magnetic material on the tape, which is moving past and in contact with the head, to align in a manner proportional to the original signal. The signal can be reproduced by running the tape back across the tape head, where the reverse process occurs – the magnetic imprint on the tape induces a small current in the read head which approximates the original signal and is then amplified for playback. Many tape recorders are capable of recording and playing back at once by means of separate record and playback heads in line or combined in one unit.

Mechanical
Modern professional recorders usually use a three-motor scheme. One motor with a constant rotation speed provides traction for the capstan. This, usually combined with a rubber pinch roller, ensures that the tape speed does not fluctuate. Of the other two motors, one applies a very light torque to the supply reel, and the other a greater torque to the takeup reel, to maintain the tape's tension. During fast winding operation the pinch roller is disengaged and the reel motors provide the necessary power. The cheapest models use a single motor for all required functions, coupled to the capstan and reel spindles as needed with mechanical clutches and belts. There are also variants with two motors, in which one motor is used for rewinding only.

remote control system

A remote control is an electronic device used for the remote operation of a machine.
The term remote control can be contracted to remote or controller. It is known by many other names as well, such as clicker, flipper or the changer. Commonly, remote controls are Consumer IR devices used to issue commands from a distance to televisions or other consumer electronics such as stereo systems DVD players and dimmers. Remote controls for these devices are usually small wireless handheld objects with an array of buttons for adjusting various settings such as television channel, track number, and volume. In fact, for the majority of modern devices with this kind of control, the remote contains all the function controls while the controlled device itself only has a handful of essential primary controls. Most of these remotes communicate to their respective devices via infrared (IR) signals and a few via radio signals. Television IR signals can be mimicked by a universal remote, which is able to emulate the functionality of most major brand television remote controls. They are usually powered by small AAA or AA size batteries.

History:

One of the earliest examples of remote control was developed in 1898 by Nikola Tesla, and described in his patent, U.S. Patent 613,809, named Method of an Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles.
In 1903, Leonardo Torres Quevedo presented the Telekino at the Paris Academy of Science, accompanied by a brief, and making an experimental demonstration. In the same time he obtained a patent in France, Spain, Great Britain, and the United States. The Telekino consisted of a robot that executed commands transmitted by electromagnetic waves. It constituted the world's first apparatus for radio control and was a pioneer in the field of remote control. In 1906, in the presence of the king and before a great crowd, Torres successfully demonstrated the invention in the port of Bilbao, guiding a boat from the shore. Later, he would try to apply the Telekino to projectiles and torpedoes, but had to abandon the project for lack of financing.
The first remote-controlled model aeroplane flew in 1932, and the use of remote control technology for military purposes was worked intensively during the Second World War, one result of this being the German Wasserfall missile.
By the late 1930s, several radio manufacturers offered remote controls for some of their higher-end models. Most of these were connected to the set being controlled by wires, but the Philco Mystery Control (1939) was a battery-operated low-frequency radio transmitter,[1] thus making it the first wireless remote control for a consumer electronics device.

The first remote intended to control a television was developed by Zenith Radio Corporation in 1950. The remote — officially called "Lazy Bones" was connected to the television set by a wire. To improve the cumbersome setup, a wireless remote control called "Flashmatic" was developed in 1955 which worked by shining a beam of light onto a photoelectric cell. Unfortunately, the cells did not distinguish between light from the remote and light from other sources and the Flashmatic also required that the remote control be pointed very accurately at the receiver.[2]

The Zenith Space Commander 600 remote control
In 1956 Robert Adler developed "Zenith Space Command", a wireless remote.[3] It was mechanical and used ultrasound to change the channel and volume. When the user pushed a button on the remote control it clicked and struck a bar, hence the term "clicker". Each bar emitted a different frequency and circuits in the television detected this noise. The invention of the transistor made possible cheaper electronic remotes that contained a piezoelectric crystal that was fed by an oscillating electric current at a frequency near or above the upper threshold of human hearing, though still audible to dogs. The receiver contained a microphone attached to a circuit that was tuned to the same frequency. Some problems with this method were that the receiver could be triggered accidentally by naturally occurring noises, and some people, especially young women, could hear the piercing ultrasonic signals. There was even a noted incident in which a toy xylophone changed the channels on these types of TVs since some of the overtones from the xylophone matched the remote's ultrasonic frequency.
The impetus for a more complex type of television remote control came in the late 1970s with the development of the Ceefax teletext service by the BBC. Most commercial remote controls at that time had a limited number of functions, sometimes as few as three: next channel, previous channel, and volume/off. This type of control did not meet the needs of teletext sets where pages were identified with three-digit numbers. A remote control to select teletext pages would need buttons for each number from zero to nine, as well as other control functions, such as switching from text to picture, and the normal television controls of volume, station, brightness, colour intensity and so on. Early teletext sets used wired remote controls to select pages but the continuous use of the remote control required for teletext quickly indicated the need for a wireless device. So BBC engineers began talks with one or two television manufacturers which led to early prototypes in around 1977-78 that could control a much larger number of functions. ITT was one of the companies and later gave its name to the ITT protocol of infrared communication