video record
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The programme examines some of the principles of computer data transmission over telephone networks and shows different types of terminal equipment which have varying data rates.
Metadata describing this Open University video programme
Module code and title: T321, Telecommunication systems
Item code: T321; 06
First transmission date: 01-05-1976
Published: 1976
Rights Statement:
Restrictions on use:
Duration: 00:18:11
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Producer: David Saunders
Contributors: Malcolm Hamer; Chris Pinches
Publisher: BBC Open University
Keyword(s): Line printer; Phase modulation; Regional network; Telephone networks; Terminal equipment; Visual Display Unit
Footage description: Chris Pinches, at the Manchester University Regional Computer Centre, introduces the programme. He points out a card reader and line printer together with their respective data rates. Malcolm Hamer, with the aid of an animation, explains the technique of phase modulation for coding computer data transmissions along telephone lines. He then displays the coded signal on an oscilloscope screen. Hamer next uses a spectrum analyser to demonstrate the need for data rate to remain within the 300 to 3,400 hertz telephone wave band if errors are not to occur at the output end. Hamer explains, with the aid of an animation, how the use of additional phase changes, to signal bit pairs, will allow an increased data rate. The spectrum analyser is then used to demonstrate that a data rate of double the previous rate can be achieved without going outside the permitted bandwidth of the telephone system. Hamer briefly lists the three main components of the data links in a computer network (two modems and a telephone channel). Chris Pinches points out several of the modems at the Manchester University Computer Centre and gives their data rates. Pinches then looks at two line printer terminals at the Centre and works out their data rates. Shots of the line printers at work. Pinches next looks at two cathode ray tube output devices which display data in alphanumeric and graphical form. Both terminals are demonstrated and their data rates calculated. Malcolm Hamer briefly discusses the nature and extent of the Manchester University computer network. A map of England shows the extent of the network. Hamer and Roy Duffy (University of Manchester Computer Centre) discuss the computing power of the Manchester system and the developments in data transmission which made such a network possible. Duffy speculates on some future developments of data transmission in computer networks.
Master spool number: 6HT/71992
Production number: 00525_5225
Videofinder number: 1347
Available to public: no