Telenet packet switching network. 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, 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. 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. 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. Hardware and software Prestel computers were based on GEC 4000 series minicomputer with small differences in the accumulation according to the function of the machine. IRC main machines were originally GEC 4082 equipped with 384 Kbytes memory core store machines, six 70 Mbyte HDD and 100 ports for 1500 initial users. The network grew to the point that in June 1980 there were four stand-alone retrieval computers in the London area with six other computers installed in pairs in Birmingham, Edinburgh and Manchester. The ten computers could output to approximately 1000 user ports, expandable to 2000. The GEC 4082 computer with 512 megabyte capacity will interconnect to the 10 and later to 20 retrieval computers to handle the data files. The initial data base consists of approximately 164,000 information pages (June, 1980) with planned update capacity of 260,000 pages. A page consists of a maximum of 960 data characters (5x7 bits each, suggesting approximately 35,000 bits per page). This arrangement effectively limited the size of the public service database to around 250,000 frames so in order to cope with planned growth by 1981 the IRC machines had been expanded by the addition of two further data drives. Each IRC computer was configured with 208 ports and so was able to support 200 simultaneous Prestel users, the remaining 8 ports being used for test and control functions. Access for the ordinary user was