Jump to content

Prestel: Difference between revisions

From Wikipedia, the free encyclopedia
Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
→Successes: Deleted "Careerdata" para (& hence this section) as: a) unsourced; b) undue weight; c) travel agents point belongs to Viewdata article as an application e.g.; d) "sold abroad" point is developed in "Other implementations" section; e) Queen's Award is buried here & needs taking up in, potentially, a new "Recognition" section.
Bagelfoc (talk | contribs)
41 edits
m Add a few links and a source for the claim of 90,000 subscribers.
Line 35: Line 35:
}}
}}


'''Prestel''' was the [[Brand#Brand names and trademark|brand name]] of a [[videotex]] service launched in the UK in 1979 by [[BT Group#Post Office Telecommunications|Post Office Telecommunications]], a division of the British [[Post Office Limited#History|Post Office]]. It had around 90,000 subscribers at its peak, and was a forerunner of the internet-based online services developed in the late 20th and early 21st centuries. Prestel was discontinued in 1994.
'''Prestel''' was the [[Brand#Brand names and trademark|brand name]] of a [[videotex]] service launched in the UK in 1979 by [[BT Group#Post Office Telecommunications|Post Office Telecommunications]], a division of the British [[Post Office Limited#History|Post Office]]. It had around 90,000 subscribers at its peak<ref>{{Cite web |title=History of Computing: Prestel |url=https://parkershaw.co.uk/blog/history-of-computing-prestel |access-date=2024-10-21 |website=Parker Shaw |language=en}}</ref>, and was a forerunner of the internet-based online services developed in the late 20th and early 21st centuries. Prestel was discontinued in 1994.


A subscriber to Prestel used an adapted TV set with a keypad or keyboard, a dedicated terminal, or a microcomputer, to interact with a central database via an ordinary phoneline. Prestel offered hundreds of thousands of pages of general and specialised information, ranging from consumer advice to financial data, as well as services such as home banking, online shopping, travel booking, [[telesoftware]], and messaging.
A subscriber to Prestel used an adapted TV set with a keypad or keyboard, a dedicated terminal, or a microcomputer, to interact with a central [[database]] via an ordinary [[Telephone line|phoneline]]. Prestel offered hundreds of thousands of pages of general and specialised information, ranging from consumer advice to financial data, as well as services such as home banking, online shopping, travel booking, [[telesoftware]], and messaging.


==Initial development==
==Initial development==

Revision as of 22:56, 21 October 2024

For the publisher, see Prestel Publishing.
For the artist, see Maria Katharina Prestel.

Prestel
Logo
DeveloperPost Office Telecommunications
Key peopleSamuel Fedida
TypeGeneral-purpose
public videotex service
Launch date1979; 46 years ago (1979)
Discontinued1994; 31 years ago (1994)
Platform(s)GEC 4000 minicomputers in a star network configuration with packet-switched connections
Operating system(s)OS4000 operating system supporting BABBAGE high-level assembly language
StatusDiscontinued
Membersc. 90,000 subscribers at peak
Pricing modelSubscription (quarterly) and usage (time spent on system, some pages, some messaging service actions)

Prestel was the brand name of a videotex service launched in the UK in 1979 by Post Office Telecommunications, a division of the British Post Office. It had around 90,000 subscribers at its peak[1], and was a forerunner of the internet-based online services developed in the late 20th and early 21st centuries. Prestel was discontinued in 1994.

A subscriber to Prestel used an adapted TV set with a keypad or keyboard, a dedicated terminal, or a microcomputer, to interact with a central database via an ordinary phoneline. Prestel offered hundreds of thousands of pages of general and specialised information, ranging from consumer advice to financial data, as well as services such as home banking, online shopping, travel booking, telesoftware, and messaging.

Initial development

Prestel was created based on the work of Samuel Fedida at the then Post Office Research Station in Martlesham, Suffolk. In 1978, under the management of David Wood, the software was developed by a team of programmers recruited from within the Post Office Data Processing Executive. As part of the privatisation of British Telecom, the team were moved into a "Prestel Division" of BT.

Database

Pages and frames

Information on Prestel was held in a database of "pages". Each page corresponded to a screenful of information, and had a unique number up to nine digits long.[a] A page could have up to 26 sub-pages, with each sub-page labelled with a letter from "a" to "z". A sub-page was called a "frame": the page itself was frame "a". Neither pages nor frames could scroll.[2]: 20–21 [3]: 2 [4]: 2 

Each frame had 24 lines of 40 characters each, like the display format used by the Ceefax and ORACLE teletext services. The top line showed the name of the Information Provider (IP), the page number, and the price.[3]: 7  The bottom line was reserved for system messages, leaving 22 lines available for the IP to present information to the user.[5]: 12 

An IP rented a three-digit number as its master page. For example, the Meteorological Office's was 209,[6]: 6  and the numbers identifying all its pages began with these digits – such as for 20971, the page for "Aviation forecasts".[7]: 1 

Single- and double-digit pages were reserved by Prestel for system information purposes, such as page 1, which showed the main index. Pages starting with 9 were for account and other system management functions: page 92, for example, showed details of a Prestel user's bill.[3]: 10 

When preparing and editing a page, an IP could use upper- and lower-case letters, digits, punctuation marks, a few arithmetic symbols, and a set of "mosaic characters" for composing rudimentary graphics.[6]: 19 [b] By embedding cursor-control characters in the page, simple animations could be produced by rewriting parts of the screen already displayed. These were called "dynamic frames".[c]

The IP's name on line 1 occupied at least 43 bytes, depending on the number of control characters involved, so the space available for the IP's data on-screen was a maximum of 877 characters[5]: 12  A line could occupy all forty of the character positions available, or be terminated early with a control character. Each control character consumed two bytes, so the more complex the page, the less information could be shown.[citation needed]

Most frames were set up to provide information. Other types were for messaging, or provided a gateway to other computer-based services. A "follow-on" type could also be specified: this caused the following frame to be automatically displayed as soon as the current frame had finished being transmitted. For dynamic frames, this provided a way to continue animations that could not fit within the number of characters available in one frame alone.[citation needed]

This follow-on frame facility was also used for telesoftware, enabling computer programs, such as those for the BBC Micro, to be downloaded from Prestel.[d]

A page could be directly linked to up to ten other pages by specifying, during editing, the number of the page whose content would be displayed when a user pressed a digit from 0 to 9 on their keypad or keyboard.[2]: 20  Double-digit links – such as "56" – were achieved by linking the first digit to an intermediate, stepping-stone frame on the IP's database: this, in turn, connected the second digit to the target page.[9]: 1 

The content of pages ranged between two poles: at one, a menu listing the topics available and the number to key to reach them, with no, or minimal, further information – referred to as an "index page"; and at the other, a screenful of information with few, if any, links to other pages – an "information page". According to Rex Winsbury, a media journalist and editorial director of Fintel, a major IP, [e] as experience with the viewdata medium grew, IPs "gave information on all or most pages, simply varying the amount according to the number of routings [links] that have to be given as well."[2]: 22 

Structures

When the public Prestel service began in 1979, a user connecting to the system was presented with the main index page. As they made and keyed successive menu choices, they moved down a subject hierarchy, from the general to the specific, to finish with the information page they sought.[10]: 61  The Post Office, academics, and the media referred to this hierarchical database arrangement as a tree structure or "inverted tree".[9]: 1 [11]: 112 [12]: col. 2 

Though simple in theory, in practice this structure could lead a user to a dead end: they might find that how a subject was described in a menu did not match what they saw on the final destination page, or formed only part of what they were looking for, or provided information without the means to look up related material. Going back up the sequence of menu choices (using the *# command) to try another series of links was limited to three steps in all.[10]: 62–63 

As Prestel developed, IPs accommodated the particularities of the different types of information and services they provided, and the expectations of their users, through the extensive use of backlinks and crosslinks between their pages. This resulted in a variety of database structures that acquired labels such as cartwheels, ring-of-rings, Chinese lanterns and lobster-pots to visualise how pages were connected.[2]: 24 [13]: 9 

Front of guide
front
Back of guide
back
Pocket guide to Prestel for medical practitioners, c. 1984. Their welcome page was 1629.[14] Laminated card, 6.9 x 11 cm

There were three basic navigation commands:[6]: 20 

  • *number# took the user directly to the first frame of the page number specified: for example, *5052# displayed the contents of 5052a onscreen;
  • # moved the user successively forward through the frames: 5052b, 5052c, and so on;
  • *# returned the user to the previous page in strict sequence, and could be repeated three times.

Keyword access was introduced in 1987, with *keyword# taking the user directly to the subject (or subject index) specified.[13]: 8 [6]: 20 

A topic index, updated daily, was published on page 199, and an IP index on page 198. A printed A‍–‍Z directory of the topics available on Prestel, with the appropriate page number to key, was sent to new users. From 1987, the topic names could also be used as keywords.[7] Every two months, users were sent a magazine, Connexions,[15] that included an updated directory, and the directory was also incorporated into the quarterly Prestel Business Directory created by the Financial Times.[16]

Information providers

There were two levels of information provider (IP): main IPs, and sub-IPs.

Charges

A main IP rented pages directly from the Post Office (initially) or British Telecom (later), and owned a three-digit node or "master page" in the database. This required an annual payment in 1982 of £5,500 for a basic package,[17]: 1  equivalent to around £29,000 in 2021.[18]

The basic IP package included 100 frames; the ability to enter and amend information, retrieve response frames, and store 10 completed response frames; staff training in editing (a two-day seminar), and a copy of the IP editing manual; and, if required, bulk update facilities and an annual print-out of frames in use. Additional frames were available, in batches of 500, for £500 a year (over £2,600 in 2021),[18] while using "Closed User Groups" (CUGs)[f] and the sub-IP facility each cost £250 annually[17]: 1  (over £1,300 in 2021).[18]

Sub-IPs – those with smaller requirements or budget – rented pages from a main IP.[19]: 130  After paying the additional £250 annual fee, a main IP could rent out individual pages at a market rate. Unlike a main IP, sub-IPs paid a per-minute charge for editing online: in 1982, this was 8p per minute from Monday to Friday between 8 am and 6 pm, and 8p per 4-minute block at all other times[17]: 1  (equivalent to around 35p as at end 2014).[18] Sub-IPs were restricted to pages under a 4 or more digit node within a main IP's area, and could only edit existing pages: they were not able to create or delete pages themselves.

Editing pages

Cherry Editing Keyboard manufactured by Cherry GmbH, connected to a Deccafax Viewdata Terminal Model VP1 manufactured (1979–1994) by Decca Radio & Television. Keyboard 11 x 50 x 31 cm, terminal 42 x 45 x 45 cm, 28 kg[20]

There were two ways to edit pages: directly, by creating or amending them using special editing keyboards while connected online to the main Update Computer; or offline, creating pages locally and uploading them in bulk. Bulk update required that pages be created offline using editing terminals that could store pages, or by using microcomputers. The pages were then either transmitted to the Update Computer online as a batch via a special dialup port and protocol, or sent on magnetic tape to the Update Centre (UDC), where they were uploaded.

Using the online editor, IPs were also able to view information about a page hidden from ordinary users, such as the time and date of its last update, whether the frame was in a Closed User Group (CUG),[f] the price-to-view (if any), and the "frame count" – the number of times the frame had been accessed.[g]

IPs and sub-IPs accessed the Edit computer using their normal ID and password, but had a separate password to access the editing facility. Bulk uploads only required the edit password and the IP's account number.

Information and services

Prestel's pre-launch promotional material focused on the general public:

Prestel is for everyone. Busy mothers can check out prices before they go shopping or their children can use Prestel to help them with their homework. Gardeners will have a constant source of information on what they should be doing at any particular time of the year. Whole families can choose and even book their holidays through Prestel. [..] Prestel will provide you with listings for theatres, cinemas, sporting events, exhibitions and just about anything else that may be going on.[21]: 3 

When the service launched in late 1979, Post Office Telecommunications had a hands-off approach towards managing whatever IPs placed on the system.[22]: 25  This changed in early 1980, when British Telecom (its successor) started targeting the business, professional and hobbyist markets via joint ventures with companies and organisations with specialised expertise.[22]: 25 

By the mid-1980s, the specialised services on Prestel included:[6]: 15–18 

  • Prestel CitiService, involving the London Stock Exchange and ICV Information Systems, targeted three groups: the business community as a whole, with mainly company information; private investors in a closed user group[f], offering regularly updated share prices; and for brokers and other investment professionals, continuously updated share prices, also in a closed user group.[23]
  • British Telecom Travel Service provided travel agents with information from tour operators, airlines, and other transport operators, and enabled online reservations. The service for other users included flight arrivals and departures, car rental, and exchange rates.
  • Prestel Farmlink packaged information for farmers from the Ministry of Agriculture, Fisheries and Food, the Meat and Livestock Commission, the Meteorological Office, and others. A link to Prestel CitiService provided farm commodity prices, and farmers could calculate, online, weekly wages and the formulation of feedstuffs.
  • Banking: the Nottingham Building Society offered Homelink, and the Bank of Scotland HOBS, the Home & Office Banking Service. Subscribers were provided with free or subsidised Prestel terminals.
  • Prestel Microcomputing offered downloadable software (telesoftware), noticeboards, newsletters, and reviews. It incorporated Micronet 800 from EMAP, Viewfax 258, and Clubspot 810.[24]
  • Prestel Education targeted schools and colleges, and provided course and careers advice, educational software, and help with using computers.
  • British Telecom Insurance Services provided financial information to insurance intermediaries and enabled them to get online quotes from major insurance companies.
  • Prestel Teleshopping was a specialised e-commerce service for the residential market, and involved Littlewoods and Kays Catalogues, among others.

Messaging

Response frames

A "response frame" enabled a user to send a message to an IP using a special preformatted page, for example to order goods or services.[19]: 133  The user's name, address, telephone number, and date could be added automatically to the message when the IP set up the response frame by means of codes which triggered extraction of key data from the users account held on the IRC computer. Initially response frames were ingathered by an IP from each IRC individually, but later the facility to collect messages from all IRCs at the UDC from where they could be ingathered centrally was implemented, and with the introduction of Mailbox, they could be retrieved from any IRC.

Mailbox

Launch version of Prestel Mailbox entry page, *7# (1983).

In 1983, the Prestel messaging service known as "Prestel Mailbox" was launched, initially hosted on the computer known as "Enterprise",and later available from all IRC computers by means of a centralised messaging computer known as "Pandora".[citation needed]

The entry page for Prestel Mailbox was *7#. This linked to pages where new messages could be composed, stored messages retrieved, and standard, pre-formatted messages completed – many designs were available, including greetings cards and seasonal messages such as valentines. To prepare a basic message, a blank message page, directly accessible via *77#, was displayed, with the sender's Mailbox number pre-filled and empty fields for entering the recipient's number and the text of the message. As messages could only occupy a single frame, there was space for up to 100 words or so, depending on any other fields present (as in pre-formatted messages) and any graphics used. After addressing (with a Mailbox number) and writing the message, the user was offered the choice of keying 1 to send it, or keying 2 to not send it. Successful dispatch led to a confirmation page; if there were problems, such as a mistake in entering the recipient's Mailbox number, an error message was displayed.[6]: 8  To send the message to more than one recipient meant re-keying the text into a fresh message frame, although some microcomputers allowed the original message to be stored and then copy-pasted instead.[4]: 29 

Screenshot of a received message. The name of the host computer, "Enterprise", is at top-right. The Mailbox numbers start with 01999, so are ex-directory. The bottom of the screen shows instructions for storing or deleting the message.[25]

Prestel Mailbox numbers were generally based upon the last 9 digits of the user's telephone number, without spaces or punctuation. For example, the Prestel Mailbox number for Prestel Headquarters which had the telephone number 01-822 2211 would be simply 018222211, while that for a user in Manchester with telephone number 061-228 7878 would be 612287878.[citation needed] In keeping with phone directory practice at the time, Prestel Mailbox numbers were published by default in a list accessible from page *486#. Ex-directory Mailbox numbers were available on request.[h]

Prestel Mailbox promotional badge, c.1983. Metal, 5.6 cm diameter

Every time a user logged into Prestel, a Mailbox banner on their Welcome page, usually flashing, would alert them if they had any new messages waiting. Similarly, upon the user's request to sign off the system via *90#, a warning would appear if any new messages had arrived, with an option to read them, before the user was allowed to disconnect. Messages were retrieved from page *930#, where they were presented to the recipient in chronological order. After reading a new message, the user had to choose between deleting the message, or saving it, before the next message was presented. Initially only three messages could be saved at any one time, and these stored messages were accessible via page *931#.

Use of the basic Mailbox service was free, that is to say there were no registration charges for owning a mailbox, or for sending new messages or for storing received messages, although even by 1984 only five messages could be saved once they had been read.

Prestel Mailbox was extended in 1984 to give access to the Telex service via "Telex Link". On *8#, the Telex Link entry page, a message could be composed, the destination country chosen, and the telex number entered before sending the telex like a standard message. Telex Link added the necessary telex codes and tried to send the message several times before confirming receipt (or failure) via Mailbox. A telex could be sent to a Mailbox user from any telex terminal by using 295141 TXLINK G, the Telex Link number, as the telex address, and entering "MBX", followed by the Prestel user's Mailbox number, as the first line of the telex. The incoming telex appeared to the Prestel recipient as an ordinary Mailbox message, with the telex number of the sender added at the top of the screen. Sending a telex cost 50p for UK destinations, £1.00 for Europe, £2.00 for North America, £3.00 for elsewhere in the world, and £5.00 for sending to ships (via INMARSAT). There was no charge for receiving one.[26]

In 1984, when there were some 70,000 users registered, up to 100,000 mailboxes and telexes were sent each week via Prestel Mailbox.[citation needed]

Mailbox upgrade

From July 1989, a new mailbox system was introduced which allowed for single messages of up to five frames in length, storing of messages prior to sending, sending to multiple recipients, either individually or via a mailing list, forwarding of messages, and requesting an acknowledgment of receipt. Whilst sending a simple mailbox using none of the new facilities remained free, all of the new options were charged at 1p per use per recipient. For the first time, the sending of spam was accounted for and permitted, albeit at 20p per recipient. In addition, the stored message facility was replaced by a summary page, which listed all the messages, both new and old, that were waiting. The user could then pick which message to view, rather than being required to read through them all in chronological order. As only the first 20 could be accessed, this effectively allowed for up to 19 messages to be stored while allowing the continued reception of new mail.[27]

A security breach of the Prestel mailbox of Prince Philip, Duke of Edinburgh and subsequent trial led to the Computer Misuse Act 1990.[citation needed]

Infrastructure

With a view to supporting the planned major expansion programme, a new Prestel infrastructure was designed around two different types of data centre: Update Centre (UDC), where IPs could create, modify and delete their pages of information, and Information Retrieval Centre (IRC), which mirrored copy of the pages is provided to end-users. In practice there only ever was one Update Centre, and this always housed just one update computer, named "Duke", but within six months of public launch there were in addition two dedicated information retrieval computers.[19]: 130 

Baynard House, Blackfriars

In those early days of the public service all the live Prestel computers were located in St Alphage House, a 1960s office block on Fore Street in the City of London. At the time the National Operations Centre (NOC) was located in the same building on the same floor. The computers and the NOC were later moved to Baynard House, (on Queen Victoria Street, also in the City of London) which acted as a combined UDC and IRC. Both types of machine, together with other development hardware, remained in service there until 1994 when the Prestel service was sold by BT to a private company.

Each IRC usually housed two information retrieval computers, although some IRCs in London only had a single machine.[19]: 130  IRCs were generally located in major telephone exchanges, rather than in BT data processing centres, to accommodate the extensive communications equipment needed. Exchange buildings could more easily house the large numbers of rack-mounted 1200/75 baud modems and associated cabling required, as well as the multiplexers from GEC,[i] which gave the modems access to the computers.[citation needed]

In the new infrastructure, IRCs were connected to the UDC in a star network configuration, originally via leased line permanent (not packet switched) connections, based on the X.25 protocol, operating at 2400 baud.[28] By mid 1981, these private circuit links had been replaced with dedicated 4-wire X25 circuits over the new public Packet Switch Stream (PSS) network operating at 4.8 kbit/s.[citation needed]

By June 1980, there were four singleton retrieval computers in London, plus six other machines installed in pairs at IRC sites in Birmingham, Edinburgh and Manchester.[29] Fully equipped IRC machines had a design capacity of 200 user ports each,[19]: 130  but these first ten machines were initially only capable of supporting approximately 1,000 users between them, expandable later to 2,000 users.[29]

By September 1980, there were five IRC machines in London plus pairs of machines at Birmingham, Nottingham, Edinburgh, Glasgow, Manchester, Liverpool and Belfast offering a total of 914 user ports. Further IRC's were planned at Luton, Reading, Sevenoaks, Brighton, Leeds, Newcastle, Cardiff, Bristol, Bournemouth, Chelmsford and Norwich by the end of 1980.[28] In some of these locations where there was insufficient Prestel traffic to warrant siting an IRC computer, the plans were to site multiplex equipment in a suitable exchange building from where connections were made over X25 to the nearest proper IRC.[citation needed] As at the end of 1980, there was actually a total of 1500 live computer ports available and by July 1981, the number of IRC computers has been expanded to 18, increasing the coverage of the telephone subscriber population from 30% to 62%.[19]: 129 

In 1982, using the multiplexor technique described above, a virtual IRC was created in Boston, Massachusetts giving access to a machine in the UK known as Hogarth in order to provide Prestel services to subscribers from across the United States via the Telenet packet switching network.[citation needed]

The Prestel Mailbox service was originally launched on Enterprise computer to support messaging solely between users on that machine and by 1984, the facility had been rolled out nationwide. This required a further type of Prestel computer dedicated to the exchange of messages. The only example of this type, which became known as Pandora,[citation needed] was co-located with the UDC in Baynard House, London.

Originally Prestel IRC computers were directly dialled by means of an ordinary telephone number (e.g., the Enterprise computer in Croydon was accessed by dialling 01 686 0311).[4]: 11  By 1984, the special short dialling codes 618 and 918 were in use in order to give access to the nearest IRC at local telephone call rates, at least across most parts of the UK.[citation needed]

In 1987, the entire local access network was being overhauled and shared with other Dialcom Group companies – users connecting and not automatically logging into Prestel would be greeted with a menu allowing access to Prestel, Telecom Gold, etc.[citation needed]

Hardware and software

Prestel's computers were based on the GEC 4000 series minicomputer. The main IRC machines were originally model GEC 4082s equipped with 384 Kbyte memory-core stores, six 70 Mbyte hard disk drives, and 100 ports. This set-up accommodated an initial 1500 Prestel users.

By June 1980, the network had grown to four individual information-retrieval computers in the London area, and six others installed in pairs in each of Birmingham, Edinburgh and Manchester, making ten in all. These ten computers could connect to around 1000 user ports, expandable to 2000. The initial database consisted of about 164,000 information pages with a planned expansion to 260,000 pages: this arrangement limited the size of the public service database to around 250,000 frames.[19]: 133  By 1981, to cope with planned growth, the IRC machines had been expanded by adding two further data drives.[citation needed]

Each IRC computer had 208 ports. With eight reserved for testing and control, a computer could support up to 200 simultaneous Prestel users. For the ordinary user, access was via an asynchronous, duplex interface provided by banks of multiplexers.[i] These, in turn, were accessed via standard modems, operating at 1200/75 bit/s, directly connected to the public phone network.[19]: 130 

By 1981, this configuration had changed, with memory doubled to 768 kbytes and data discs reduced to six, corresponding to the number at the IRC machines and with just a single transaction disc.[19]: 131 

Besides the multiplexers required to support 1200/75 dial-up access, the Update Centre machines were also connected to special modems that handled online bulk updating by IPs. Banks of 300/300 bit/s full-duplex asynchronous V.21 modems supported direct IP-computer-to-Prestel-computer links, while 1200 bit/s half-duplex V.23 modems supported access by IPs using editing terminals that stored frames offline before uploading them. In addition, twin 9-track NRZI tape decks of 800 bytes/inch capacity were provided for bulk offline updates.[19]: 131 

GEC 4000 series computers at GEC Computers' Dunstable Development Centre, 1991

Though categorised as a minicomputer, GEC 4000 series machines were large: one occupied several standard computer cabinets each standing 6 feet (1.8 m) high by 2 feet (0.61 m) wide. The CDC 9762 hard disc drives were housed separately in large, stand-alone units about the size of a domestic washing machine.[j] A GEC machine cost over £200,000 at standard prices, in addition to which were the costs of the associated communications equipment. Combining the two to assemble a single IRC was a major undertaking, and took some 15 months from order placement to commissioning.[19]: 132 

GEC 4000 series computers could run one of several operating systems: in practice, though, Prestel machines ran on OS4000 exclusively. OS4000 was developed by GEC and supported BABBAGE,[citation needed] the high-level assembler in which all Prestel software was written.

In 1987, a Prestel Admin computer was introduced to support the user registration process: it handled capturing a new user's details from the paper Prestel application form, transferring the data to the relevant Prestel computer, and then printing the welcome letter to be sent to the user concerned.[k]

Monitoring

Users' connections to Prestel were monitored by a device known as VAMPIRE – "Viewdata Access Monitor and Priority Incident Reporting Equipment". Via private circuits connected to an IRC computer's ports, this produced a continuously updated display on a monitoring screen at the Prestel Regional Centre responsible for an IRC.[19]: 131  The screen showed a matrix of small squares, each corresponding to a port on an IRC computer. Free ports were green, occupied ones yellow, incoming calls-to-connect by Prestel users were pale blue, and faulty ports red. In this way, the overall status of an IRC machine could be summarised and seen at a glance.

Public take-up

Writing in early 1979 about the test service that had launched in October 1978, a PTO executive concluded that:

"The strengths of viewdata include its visual attractiveness, its ease of use, low cost and its wide range of applications. Its weaknesses include its small information window, unsophisticated search methods, its limited storage capacity and its lack of computer power for users. How rapidly viewdata will become established, and the exact role it will fulfil, is as yet a matter of speculation."[30]

While teletext services were provided free of charge, and were encoded as part of the regular television transmissions, Prestel data were transmitted via telephone lines to a set-top box terminal, computer, or dedicated terminal. While this enabled interactive services and a crude form of e-mail to be provided, gaining access to Prestel also involved purchasing a suitable terminal, and arranging with a Post Office engineer for the installation of a connection point known as a Jack 96A.[citation needed] (From the early 1980s, the "New Plan" sockets were fitted as standard on new lines and on any change of rented handset, and terminals or modems then required no special connections.)

Thereafter it was necessary to pay both a monthly subscription and the cost of local telephone calls. On top of this, some services (notably parts of Micronet 800) sold content on a paid-for basis. Each Prestel screen carried a price in pence in the top right-hand corner. Single screens could cost up to 99p.

The original idea was to persuade consumers to buy a modified television set with an inbuilt modem and a keypad remote control in order to access the service, but no more than a handful of models were ever marketed and they were prohibitively expensive. Eventually set-top boxes were made available, and some organisations made these available as part of their subscription, for example branded Tandata terminals were provided by the Nottingham Building Society for its customers, who could make financial transactions via Prestel.

Prestel terminal

Because the communication over telephone lines did not use any kind of error correction protocol, it was prone to interference from line noise which would result in garbled text. This was particularly problematic with early home modems which used acoustic couplers, because most home phones were hard-wired to the wall at that time.

Regardless of the hardware choice Prestel was an expensive proposition, and as a result, Prestel only ever gained a limited market penetration among private consumers, achieving a total of just 90,000 subscribers, with the largest user groups being Micronet 800 with 20,000 users and Prestel Travel with 6,500 subscribers.

The costs for businesses interested in publishing on Prestel were also expensive. This ensured that only the largest or most forward thinking companies were interested in the service.

During the daytime, when business usage was high, there was a per-minute charge to use Prestel, but in the evenings and weekends, traditionally the quiet times, it was free apart from the telephone call. With Micronet being so popular, suddenly the quiet times became fairly busy.

The original Prestel system, designed for cost effectiveness and simplicity, employed a rudimentary graphic capability known as serial mosaics. Through juxtaposition of the special mosaic characters, crude but recognizable graphic representations could be made on the screen. This graphic scheme had its limitations. To change colours between two mosaic graphic characters or between any two characters in general, a colour change command was required. This command signal, however, physically occupied a blank space on the screen.

Having developed Prestel as a way of maximising usage of existing telephone lines, the British Post Office and subsequently British Telecom sought to "provide only the framework" for the service, delegating the provision of information to information providers. Nevertheless, considerable investment was required in the infrastructure to provide such a service. With information providers needing to pay rental charges and with users needing to pay installation and rental fees, such an investment was considered likely to pay off handsomely for BT and that they would be "cleaning up" by providing an interactive service that, in contrast to teletext services such as Ceefax and Oracle, could support a range of commercial activities. A "mass public service" was envisaged, with considerable public take-up, but a lack of compelling content and services gave domestic users in particular the impression of Prestel being something that "would cost them a lot for relatively little". Thus, Prestel became more like "a fragmented series of computer-linked private systems" used and run by various companies such as American Express and Thomas Cook, for whom adoption of the technology made sense operationally. Nevertheless, it was predicted that eventually, "Prestel - or another viewdata system - will be ubiquitous".[31]

Other implementations

The Prestel system was customised and resold by GEC Computers to several other countries, including: Austria, Australia, Germany, Hong Kong, Hungary, Italy, Malaysia, Netherlands, New Zealand, Singapore, and the former Yugoslavia.[citation needed]

Telecom Australia re-branded their system Viatel, with the centre of operations in Windsor, Melbourne, Australia. During the Black Monday stock market crash the system's stock trading system was highly used. The system in Italy run by SIP was heavily used during the 1990 FIFA World Cup for reporting the match progress and scores. The Singapore system provided a much higher receive bandwidth than was available over dial-up modems at the time by broadcasting the return frames using the Teletext technique of embedding them in broadcast television signals. Four VHF TV channels were dedicated to this with all the scan lines used for Teletext encoding, which enabled the system to provide a feature called Picture Prestel to convey higher resolution images. The Yugoslav system was based in Zagreb, with additional IRCs located in Rijeka, Ljubljana, and Split.[citation needed]

The American Viewtron videotex service was modelled after Prestel.[citation needed]

See also

Notes

  1. ^ I.e, page numbers could run from 0 to 999999999.
  2. ^ This was in line with a variant of the ISO/IEC 646 and CCITT standards and became formalised in the 1981 CEPT videotex standard as the CEPT3 profile.[8]
  3. ^ Dynamic frames could not be created online: their preparation required specialist software and then uploading via the "bulk update" facility. No timing options were available beyond those imposed by the transmission speed, which was usually 1200 baud.
  4. ^ The first few frames acted as headers. For example, a program would be described on frames 70067a and b, while frame c gave the number of subsequent frames containing the program, and a checksum.The telesoftware program itself started in frame d. To verify a successful download, software compared the checksum with a value calculated from the result of downloading all the frames required. If the check failed, the program had to be downloaded again.[citation needed]
  5. ^ Fintel was a joint venture between the Financial Times and Extel.
  6. ^ a b c A Closed User Group, or CUG, was a group of Prestel users, set up by an Information Provider, with access to confidential information.[6]: 18 
  7. ^ The frame count was not cumulated over all IRCs, but related only to the computer being viewed at the time: calculating national access counts was a manual exercise.
  8. ^ Ex-directory Prestel Mailbox numbers used a dummy phone number format starting with 01999 and later, 01111.[citation needed]
  9. ^ a b The multiplexers were GEC 16-port Multi-Channel Asynchronous Communications Control Units (MCACCU).
  10. ^ The 70 Mbyte capacity hard discs were removable. Each consisted of a stack of five, 14-inch (36 cm) diameter platters, standing 4 inches (10 cm) high, that could be lifted in and out of the drive unit.
  11. ^ The Prestel Admin computer, which was also based on GEC 4082 equipment, was the first to be equipped with the 1 Mbyte of memory needed to support the use of the Rapport relational database product supplied by Logica.

References

  1. ^ "History of Computing: Prestel". Parker Shaw. Retrieved 21 October 2024.
  2. ^ a b c d Winsbury, Rex (1979). The Electronic Bookstall : Push-button publishing on videotex: a critical study of Prestel in Britain. London: International Institute of Communications. ISBN 978-0-904-77610-2. OCLC 5507588.
  3. ^ a b c British Telecom (September 1982). "Prestel" (Customer brochure). London: Prestel Public Relations. Prestel P526 9/82.
  4. ^ a b c Acorn Computers (March 1984). "Prestel System User Guide – BBC Micro". Retrieved 7 October 2024 – via Internet Archive.
  5. ^ a b British Telecom (November 1981). "Prestel Bulk Update Technical Specification". Ref. 14 9 81p. Retrieved 7 October 2024 – via Internet Archive.
  6. ^ a b c d e f g British Telecom (1987). "Prestel Customer Handbook". Retrieved 7 October 2024 – via Internet Archive.
  7. ^ a b British Telecom (1 September 1987). "Prestel Start-Up Directory" (handbook). London: Prestel.
  8. ^ "Terminal Equipment (TE): videotex presentation layer protocol, videotex presentation layer data syntax" (PDF). Sophia Antipolis: ETSI. November 1990. ETS 300 072. Retrieved 9 October 2024.
  9. ^ a b Williams, Ederyn (18 July 1978). "Database Organisation and Information Retrieval – a discussion paper" (PDF). www.whatdotheyknow.com. BL: SGV 78/10. PO: PO-IP CP-26. Retrieved 14 October 2024. p. 1: The database was initially organised on the 'tree principle', in which pages were organised into a single massive tree, and page access was presumed to be primarily through a series of single digit choices. Note: this Post Office document was published by WhatDoTheyKnow as part of the outcome of a Freedom of Information request made to The British Library in February 2010.
  10. ^ a b Orna, Elizabeth (1986). "Information management by design: improving information retrieval on Prestel". Information Design Journal. 5 (1): 61–68. doi:10.1075/idj.5.1.orn. ISSN 1569-979X.
  11. ^ Storey, I. N. J. (1982). "The future of videotex systems – a personal view". Journal of Information Science. 4 (2–3): 111–115. doi:10.1177/016555158200400207. ISSN 0165-5515.
  12. ^ Schofield, Jack (13 September 1984). "How the Post Office failed to deliver". Guardian. p. 17. The tree structure means a large proportion of the frames are simply 'routeing' frames. They contain no useful information, but simply direct you on the long route to where that information is held. [column 2]
  13. ^ a b Yeates, Robin (April 1988). "Prestel indexing from the user's point of view". The Indexer. 16 (1): 7–10. doi:10.3828/indexer.1988.16.1.3. ISSN 1756-0632.
  14. ^ "Short progress report: Present and potential uses of Prestel by the medical profession". Medical Informatics. 7 (2): 141–142. 1982. doi:10.3109/14639238209010707.
  15. ^ "Connexions [cover]". Centre for Computing History. British Telecom. April–May 1988. CH24135. Retrieved 16 October 2024.
  16. ^ "Prestel Business Directory [cover]". Centre for Computing History. Financial Times Business Publishing. October 1981. ISSN 0142-5102. OCLC 225634964. CH56750. Retrieved 16 October 2024.
  17. ^ a b c British Telecom (October 1982). "Information Provider (IP) Charges and User Charges". Retrieved 8 October 2024 – via Internet Archive.
  18. ^ a b c d "Five Ways to Compute the Relative Value of a UK Pound Amount, 1270 to Present". The MeasuringWorth Foundation. Retrieved 9 October 2024.
  19. ^ a b c d e f g h i j k l Broadhead, W. R. (July 1981). "Prestel: The First Year of Public Service". Post Office Electrical Engineers' Journal. 74 (2): 129–133. Retrieved 7 October 2024 – via Internet Archive.
  20. ^ "Deccafax Viewdata Terminal Model VP1, 1979-1994, and Cherry Editing Keyboard". Science Museum Group Collection Online. Science Museum Group. 23 June 2014. Object number 1994-1169: donated by House of Commons. Retrieved 5 October 2024.
  21. ^ "Prestel" (brochure). London: Post Office Telecommunications. January 1979.
  22. ^ a b Butler Cox (January 1985). "Videotex in Europe" (PDF). Archives of IT. Butler Cox Report Series #19. London: Butler Cox & Partners. OCLC 12808197. Retrieved 17 October 2024.
  23. ^ "CitiService doubles its speed to meet demand". CITINEWS : The newsletter of Prestel CitiService. Vol. 1, no. 3. ICV Information Systems. Winter 1985–1986. p. 1.
  24. ^ Prestel Microcomputing (May 1984). "PRESTEL MICROCOMPUTING will add a new dimension to your home computing" (letter). British Telecom.
  25. ^ Ashton, Jane (host) (7 June 1984). "Using Prestel". Database. 3:08 minutes in. Thames TV – via YouTube.
  26. ^ "Mailbox Charges". British Telecom. June 1990. Retrieved 9 October 2024 – via Internet Archive.
  27. ^ a b Scott, Barry (September 1980). Viewdata and Training: What, Where and How Much (PDF) (Report). Technical Report No. 9. Burlington: Digital Equipment Corporation Educational Services. p. 7. Retrieved 8 October 2024.
  28. ^ a b Bloom, L. R.; Hanson, A. G.; Linfield, R. F.; Wortendyke, D. R. (October 1980). "Section 2.2: The United Kingdom". Videotex Systems and Services (PDF) (Report). Boulder: U.S. Department of Commerce. p. 18. NTIA Report 80-50. Archived from the original (PDF) on 6 June 2011. Retrieved 8 October 2024.
  29. ^ Williams, Ederyn (April 1979). "Strengths and Weaknesses of Prestel". Computer Communications. 2 (2): 56–59. doi:10.1016/0140-3664(79)90121-X.
  30. ^ McLaren, Ian (May 1982). "Head, Heart, Hand - and Screen". Design. pp. 50–54. Retrieved 14 March 2022.

Further reading

  • Prestel at Celebrating the Viewdata Revolution
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Prestel&oldid=1252567523"