[4][5]: 146 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.

In September 1982, to mark Information Technology Year,[b] the Royal Mail issued two commemorative stamps, one of which featured a Prestel TV set and keyboard.

[10] Further demonstrations followed, and based on the favourable reactions of TV manufacturers and potential providers of information and services, the Post Office decided to run a pilot trial.

[15]: 22–23  The full commercial service launched in September 1979;[5]: 115  the director of Prestel stated that there were over 130,000 pages in the database and 1363 "sets" [sic] connected to the system at the start of that month.

[19] Writing in the winter 1980/81 issue of British Telecom Journal, Prestel's public relations manager stated there were over 7,500 sets attached to the system, 170,000 frames in use, and more than 400 IPs and sub-IPs.

"[29] In mid-1984, the UK Department of Trade and Industry issued a booklet stating that the availability of travel information, the launch of Micronet 800, and the provision nationwide of the messaging service, Mailbox, had contributed to a rise to 45,000 attached terminals by June of that year.

1.15 After another year, in mid-1985, The Times stated there were 53,000 "terminals, adapted televisions, microcomputers or specially designed units" attached to Prestel, with residential users now accounting for 45% of the total.

[5]: 145  The Guardian attributed this to the introduction by British Telecom of an off-peak Prestel time-charge in mid-1988, discouraging the use of Micronet's popular "Chatline" service.

[37] The Times agreed, and also pointed to a steep rise in subscription charges, opining that "BT's failure to provide even this committed group with an economic ... service means that Prestel is destined ... for businesses.

"[38] The closure in April 1991 of Homelink, the home banking service launched in 1983 by the Nottingham Building Society,[39]: 1  also contributed to shrinking the number of Prestel subscribers.

[46]: 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.

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.

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.

[53]: 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.

[57]: 9  This resulted in a variety of database structures[17]: 104–105  that acquired labels such as cartwheels, ring-of-rings, Chinese lanterns and lobster-pots to help visualise how pages were connected.

[66]: 3  Other factors to be taken into account included the traffic pattern (i.e., the expected volume and frequency of data flows), the response time required (as perceived by a user), the size of the database to be accessed, and the changeability of the information stored.

[31]: 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.

[93] Several types of Prestel terminal were produced:[31]: 75–77 In March 1979, the Post Office launched a limited "London Residential Service" for subscribers in the capital.

This was based on the computer used in an earlier test phase to both store the Prestel database and enable IPs to make updates to their pages.

[citation needed] By June 1980, the network had grown to four individual information-retrieval computers in London, and six others installed in pairs in each of Birmingham, Edinburgh and Manchester, making ten in all.

Further IRCs were planned in Luton, Reading, Sevenoaks, Brighton, Leeds, Newcastle, Cardiff, Bristol, Bournemouth, Chelmsford and Norwich by the end of 1980.

[citation needed] In late 1981, an IRC called Jefferson opened in Boston, Massachusetts, giving US subscribers access to Prestel via the American Telenet packet-switched network.

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.

Writing in early 1979 about the test service that had launched in October 1978, a Post Office 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.

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 expensive.

Eventually set-top boxes became available, and some organisations supplied these as part of their subscription package: for example, branded Tandata terminals were provided by the Nottingham Building Society for its customers, who could make financial transactions via Prestel.

[citation needed] Because the transmission of Prestel over telephone lines did not use an error-correction protocol, it was prone to interference from line-noise, which would result in garbled text.

"[100] Prestel software and knowhow was sold to several countries, including Austria,[101] Australia,[102] former West Germany,[103] the then-British colony of Hong Kong,[21]: 7, 8  Hungary, Italy,[104] Malaysia,[105] the Netherlands, New Zealand, Singapore,[106] and former Yugoslavia.