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Videophone

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Video Phone
Video Phone

A videophone is a telephone with a video screen, and is capable of full duplex (bi-directional) video and audio transmissions for communication between people in real-time. It is the earliest form of videotelephony.

At the dawn of the technology, videotelephony also included image phones which would exchange still images between units every few seconds over conventional Plain old telephone service(POTS)-type telephone lines, essentially the same as slow scan TV systems.

Currently videophones are particularly useful to the deaf and speech-impaired who can use them with sign language and with a video relay service, and also to those with mobility issues or those who are located in distant places and are in need of telemedical or tele-educational services.


Contents

Descriptive names and terminology

The name videophone is not as standardized as its earlier counterpart, the telephone, resulting in a variety of names and terms being used worldwide, and even within the same region or country. Videophones are also known as videotelephones (or video telephones) and often by an early trademarked name "Picturephone", which was the world's first commercial videophone produced in volume. The compound name 'videophone' slowly entered into general use after 1950,[1] although 'video telephone' likely entered the lexicon earlier after 'video' was coined in 1935.[2]

Videophone calls (or 'videocalls'), differ from videoconferencing in that they expect to serve individuals, not groups. However that distinction has becoming increasingly blurred with technology improvements such as increased bandwidth and sophisticated software clients that can allow for multiple parties on a call. In general everyday usage the term videoconferencing is now frequently used instead of videocall for point-to-point calls between two units. Both videophone calls and videoconferencing are also now commonly referred to as a 'video link'.

Webcams are popular, relatively low cost devices which can provide live video and audio streams via personal computers, and can be used with many for video calls.[3]

A videoconference system is generally higher cost than a videophone and deploys greater capabilities. A videoconference (also known as a videoteleconference) allows two or more locations to communicate via live, simultaneous two-way video and audio transmissions. This is often accomplished by the use of a multipoint control unit (a centralized distribution and call management system) or by a similar non-centralized multipoint capability embedded in each videoconferencing unit. Again, technology improvements have circumvented traditional definitions by allowing multiple party videoconferencing via web-based applications.[4][5][6]

Early history

Barely two years after the telephone was first patented in the United States, an early concept of a combined videophone/wide-screen television called a telephonoscope was conceptualized in the popular periodicals of the day. It was also mentioned in various early science fiction works such as Le Vingtième siècle: La vie électrique (The 20th Century: The Electrical Life) and other works written by Albert Robida, and was also sketched in various cartoons by George du Maurier as a fictional invention of Thomas Edision. One such sketch was published on December 9, 1878 in Punch magazine.[7][8][9] The term telectroscope was also used in 1878 by French writer and publisher Louis Figuier, to popularize an invention wrongly interpreted as real and incorrectly ascribed to Alexander Graham Bell.[10]


In April 1891, Alexander Graham Bell did actually record conceptual notes on an electrical radiophone, which discussed "....the possibility of seeing by electricity" using devices that employed tellurium or selenium imaging components.[11] Bell wrote, decades prior to the invention of the image dissector:

"Should it be found... [that the image sensor] is illuminated, then an apparatus might be constructed in which each piece of selenium is a mere speck, like the head of a small pin, the smaller the better. The darkened selenium should be placed in a cup-like receiver which can fit over the eye… Then, when the first selenium speck is presented to an illuminated object, it may be possible that the eye in the darkened receiver, should perceive, not merely light, but an image of the object… "[11]

Bell went on to later predict that: "...the day would come when the man at the telephone would be able to see the distant person to whom he was speaking."[12][13]

The compound name 'videophone' slowly entered into general usage after 1950,[1] although 'video telephone' likely entered the lexicon earlier after 'video' was coined in 1935.[2] Prior to that time there appeared to be no standard terms for 'video telephone', with expressions such as 'sight-sound television system' , 'visual radio' and nearly 20 others (in English) being used to describe the marriage of telegraph, telephone, television and radio technologies employed in early experiments.[14][15][16]

One technological precursor to the videophone was the teleostereograph machine developed by AT&T's Bell Labs in the 1920s, which was a forerunner of today's fax (facsimile) machines. By 1927 AT&T had created its earliest electro-mechanical videophone which operated at 18 frames per second and occupied half a room full of equipment cabinets.[17] An early U.S. test in 1927 had their then-Commerce Secretary Herbert Hoover address an audience in New York City from Washington, D.C.; although the audio portion was two-way, the video portion was one-way with only those in New York being able to see Hoover.[16]

First public video telephone service

The world's first public video telephone service was developed by Dr. Georg Schubert and opened by the German Reichspost in 1936,[18][19][20] but which quickly closed in 1940 due to the WWII. In that service trial, video telephone lines linked Berlin to Nuremberg, Munich, and Hamburg, with terminals integrated within public telephone booths and transmitting at the same resolution as the first German TV sets, at 440 lines. The service was offered to the general public who had to simultaneously visit special post office videotelephone booths in their respective cities.

AT&T Picturephone

In the United States AT&T's Bell Labs conducted extensive research and development of videophones, leading to public demonstrations of its trademarked Picturephone product and service in the 1960s, including displays at the 1964 New York World's Fair.[21] The demonstration units usually used small oval housings on swivel stands, intended to stand on desks. Similar AT&T Picturephone units were also featured at the Telephone Association of Canada Pavilion (the 'Bell' Pavilion) at Expo 67, an International World's Fair held in Montreal, Canada in 1967.[21][22][23] Demonstration units were available at these fairs for the public to test, with fair-goers permitted to make videophone calls to volunteer recipients at other locations.

The United States would not see its first public video telephone booths until 1964, when AT&T installed their earliest commercial videophone unit, the Picturephone Mod I, in public booths in three cities: New York, Washington, D.C. and Chicago.[17] Picturephone booths were set up in New York's Grand Central Station and elsewhere. With fanfare, Picturephones were also installed in offices of Westinghouse in Pittsburgh, and at other progressive companies. However the use of reservation time slots and their initial cost of US$16 per three minute call at public booths greatly limited their appeal to the point that they were discontinued by 1968.[12][17]

Unrelated difficulties at New York Telephone also slowed AT&T's efforts, and few customers signed up for the service in either city. A CNN report on 6 September 2001 stated that Picturephone service only had a total of 500 subscribers at its peak, and the service faded away in the 1970s. AT&T's initial Mod I and its upgraded Picturephone Mod II programs,, researched principally at its Bell Labs, spanned 15 years and consumed US$500 million, eventually meeting with commercial failure.[24] AT&T concluded that its early videophone was a "concept looking for a market" and discontinued its Picturephone service in the late 1970s.[24] The research and development programs conducted by Bell Labs were highly notable for the beyond-the-state-of-the-art results produced in materials science, advanced telecommunications, microelectronics and information technologies.

Color on AT&T's Picturephone was not employed with their early models. These Picturephone units packaged Plumbicon cameras and small CRT displays within their housings. The cameras were located atop their screens to help users see eye to eye. See this section for more information on Picturephone technology. Later generation display screens were larger than in the original demonstration units, approximately six inches (15 cm) square in a roughly cubical cabinet.

AT&T would then market its VideoPhone 2500 to the general public from 1992 to 1995 with prices starting at US$1,500 and later dropping to $1,000,[25] again with very little commercial success.

Other early devices: 1976–1999

The Lumaphone was developed and marketed by Atari and Mitsubishi in 1985. Similar to Bell Labs' very early image transfer phone of 1956, it could transmit still images every 3–5 seconds over analog plain old telephone service(POTS) lines, and could also be connected to a regular TV or monitor for improved teleconferencing. A larger video image was available by attaching its optional VisiTel LU-500 display.[26][27]

The Intellect was a neo- or prototype wireless videophone. It was developed in 1993 by inventor Daniel A. Henderson, and featured still image and non-live video clip transfers.[28][29] The pioneering system and device were designed to receive pictures and video data sent from an originator to a message center for transmission and display to a wireless device such as a cellular telephone.[30][31]

The Intellect was essentially a cell phone handset with a large black and white display that could show still images and video clips downloaded remotely from a computer via a wireless transmitter. The data transfer protocols pioneered in the Intellect design were later deployed with the common camera phones released in the early 2000s.[29] However, the complete integration of the cellular phone, digital camera and its wireless transmission infrastructure would take a few more years to complete. The prototype models were donated to the Smithsonian's National Museum of American History in 2007.[32][33]

General lack of public acceptance

Early [[AT&T]] Picturephones had few users, in part because the service was relatively expensive, approximately US$90 per month in 1974. However as modern technology reduced the costs to nominal (see: webcams), videophone calling continued to be used marginally. This contrasts to many early, overly optimistic views that videotelephony would become ubiquitous.

One reason may be that even today videophone calling is often a poor analog for direct face-to-face conversation. Videophone users also commonly look at the video screen and not at the video camera, preventing users from having direct eye-to-eye contact, as the video cameras are usually positioned away from the screen.

Another reason may be that people actually desire less fidelity in their communication, as evidenced by the popularity of written conversation (i.e. texting and instant messaging, which are commonly available on all video-enabled cell phones and webchat programs). Additionally, some people simply did not want to be seen at home—a videophone was viewed as an intrusion.

Although it could also be argued that for users who would benefit greatly from videophone services (e.g. members of a family living far apart and who may have a strong desire, but little opportunity for face-to-face conversations), costs are still largely prohibitive for mobile videophone calls: inexpensive solutions for such calls (such as on Hutchison 3's Skype enabled cell phones) only cover a handful of countries as of late 2008.

Current usage

The widest deployment of video telephony now occurs in mobile phones, as nearly all mobile phones supporting UMTS networks can work as videophones using their internal cameras, and are able to make video calls wirelessly to other UMTS users in the same country or internationally. As of the second quarter of 2007, there are over 131 million UMTS users (and hence potential videophone users), on 134 networks in 59 countries.

Videophones are increasingly used in the provision of telemedicine to the elderly and to those in remote locations, where the ease and convenience of quickly obtaining diagnostic and consultative medical services are readily apparent.[34] In one single instance quoted in 2006: "A nurse-led clinic at Letham has received positive feedback on a trial of a video-link which allowed 60 pensioners to be assessed by medics without travelling to a doctor's office or medical clinic."[34] A further improvement in telemedical services has been the development of new technology incorporated into special videophones to permit remote diagnostic services, such as blood sugar level, blood pressure and vital signs monitoring. Such units are capable of relaying both regular audiovideo plus medical data over either standard (POTS) telephone or newer broadband lines.[35]

Videotelephony has also been deployed in corporate teleconferencing, also available through the use of public access videoconferencing rooms.

Today the principles, if not the precise mechanisms of a videophone are employed by many users worldwide in the form of webcam videocalls using personal computers, with inexpensive webcams, microphones and free videocalling web client programs. Thus an activity that was disappointing as a separate service has found a niche as a minor feature in software products intended for other purposes.

A videophone can also be created by using an old or inexpensive computer and dedicating it to run as a video softphone. This shows that some users may want to use use conventional videophones, but are likely to trade ease of use for lower costs.

Some have argued that unless conventional videophones add considerable value at low cost, and as long as less expensive alternatives (such as webphones) are available, it will be unlikely that dedicated videophones will become popular.

Sign language communications via videotelephony

Main articles: Video Relay Service, a telecommunication service for deaf, hard-of-hearing and speech-impaired (mute) individuals communicating with hearing persons at a different location, and Video Remote Interpreting, used where deaf/hard-of-hearing/mute persons are in the same location as their hearing parties

One of the first demonstrations of the ability for telecommunications to help sign language users communicate with each other occurred when AT&T's videophone (trademarked as the 'Picturephone') was introduced to the public at the 1964 New York World's Fair –two deaf users were able to freely communicate with each other between the fair and another city.[25] Various other organizations have also conducted research on signing via videotelephony.

Using such video equipment, the deaf, hard-of-hearing and speech-impaired can communicate between themselves and with hearing individuals using sign language. The United States and several other countries compensate companies to provide 'Video Relay Services' (VRS). Telecommunication equipment can be used to talk to others via a sign language interpreter, who uses a conventional telephone at the same time to communicate with the deaf person's party. Video equipment is also used to do on-site sign language translation via Video Remote Interpreting (VRI). The relative low cost and widespread availability of 3G mobile phone technology with video calling capabilities have given deaf and speech-impaired users a greater ability to communicate with the same ease as others. Some wireless operators have even started free sign language gateways.

Sign language interpretation services via VRS or by VRI are useful in the present-day where one of the parties is deaf, hard-of-hearing or speech-impaired (mute). In such cases the interpretation flow is normally within the same principal language, such as French Sign Language (FSL) to spoken French, Spanish Sign Language (SSL) to spoken Spanish, British Sign Language (BSL) to spoken English, and American Sign Language (ASL) also to spoken English (since BSL and ASL are completely distinct), etc.... Multilingual sign language interpreters, who can also translate as well across principal languages (such as to and from SSL, to and from spoken English), are also available, albeit less frequently. Such activities involve considerable effort on the part of the translator, since sign languages are distinct natural languages with their own construction, semantics and syntax, different from the aural version of the same principal language.

With video interpreting, sign language interpreters work remotely with live video and audio feeds, so that the interpreter can see the deaf or mute party, and converse with the hearing party, and vice versa. Much like telephone interpreting, video interpreting can be used for situations in which no on-site interpreters are available. However, video interpreting cannot be used for situations in which all parties are speaking via telephone alone. VRI and VRS interpretation requires all parties to have the necessary equipment. Some advanced equipment enables interpreters to remotely control the video camera, in order to zoom in and out or to point the camera toward the party that is signing.


Technology

Bandwidth requirements

Videophones have historically employed a variety of transmission and reception bandwidths, which can be understood as data transmission speeds. The lower the transmission/reception bandwidth, the lower the data transfer rate, resulting in a more limited and poorer image quality. Data transfer rates and live video image quality are related, but are also subject to other factors such as data compression techniques. Some early videophones employed very low data transmission rates with a resulting sketchy video quality.

Broadband bandwidth is often called "high-speed", because it usually has a high rate of data transmission. In general, any connection of 256 kbit/s (0.256 Mbit/s) or greater is more concisely considered broadband Internet. The International Telecommunication Union Standardization Sector (ITU-T) recommendation I.113 has defined broadband as a transmission capacity at 1.5 to 2 Mbit/s. The United States Federal Communications Commission definition of broadband is 768 kbit/s (0.8 Mbit/s).

Currently, adequate video for some purposes becomes possible at data rates lower than the ITU-T broadband definition, with rates of 768 kbit/s and 384 kbit/s used for some video conferencing applications, and rates as low as 100 kbit per second used for videophones using H.264/MPEG-4 AVC compression protocols. The newer MPEG-4 video and audio compression format can deliver high-quality video at 2 Mbit/s, which is at the low end of cable modem and Asymmetric Digital Subscriber Line(ADSL) broadband performance.

Picturephone technology

The Picturephone's video bandwidth was 1 MHz with a vertical scan rate of 30 Hz, horizontal scan rate of 8 kHz, and about 250 visible scan lines. The equipment included a Speakerphone hands free telephone, with an added box to control picture transmission. Each Picturephone line used three twisted pairs of ordinary telephone cable, two pairs for video and one for audio and signaling. Cable amplifiers were spaced about a mile apart (1.6 kilometres) with built-in six-band adjustable equalization filters. For distances of more than a few miles, the signal was digitized at 2 MHz and 3 bits per sample Differential Pulse Code Modulation(DPCM), and transmitted on a T-2 carrier.

The original Picturephone system used contemporary crossbar and multi-frequency operation. Lines and trunks were six wire, one pair each way for video and one pair two way for audio. MF address signaling on the audio pair was supplemented by a Video Supervisory Signal (VSS) looping around on the video quad to ensure continuity. More complex protocols were later adopted for conferencing.

To deploy Picturephone service new wideband crossbar switches were designed and installed into the Bell System's 5XB switch offices, this being the most widespread of the relatively modern kinds. Hundreds of technicians attended schools to learn to operate the Cable Equalizer Test Set and other equipment, and to install Picturephones.

AT&T later marketed the VideoPhone 2500 to the general public from 1992 to 1995. It was limited by analog phone line connection speeds of about 19 Kilobits per second, the video portion being 11,200 bits/s, and with a maximum frame rate of 10 frames per second, but typically much lower. The VideoPhone 2500 used proprietary technology protocols.

Call setup

Videoconferencing in the late 20th century was limited to the H.323 protocol (notably Cisco's Skinny Client Control Protocol(SCCP) implementation was an exception), but newer videophones often use Session Initiation Protocol(SIP), which is often easier to set up in home networking environments. H.323 is still used, but more commonly for business videoconferencing, while SIP is more commonly used in personal consumer videophones. A number of call-setup methods based on instant messaging protocols such as Skype also now provide video. The principal open systems SIP source is Counterpath Corp., which provides support for British Telecom, Deutsche Telekom, Sprint, Telmex, AT&T's Callvantage, and the unified communicator of Cisco and Verizon.

Another protocol used by videophones is H.324, which mixes call setup and video compression. Videophones that work on regular phone lines typically use H.324, but the bandwidth is limited by the modem to around 33 kbit/s, limiting the video quality and frame rate. A slightly modified version of H.324 called 3G-324M defined by 3GPP is also used by some cellphones that allow video calls, typically for use only in UMTS networks.

There is also H.320 standard, which specified technical requirements for narrow-band visual telephone systems and terminal equipment, typically for videoconferencing and videophone services. It applied mostly to dedicated circuit-based switched network (point-to-point) connections of moderate or high bandwidth, such as through the medium-bandwidth ISDN digital phone protocol or a fractionated high bandwidth T1 lines. Modern products based on H.320 standard usually support also H.323 standard.[36]


References

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