Available online
Description
The programme demonstrates two methods of multiplexing used in the British telephone system - frequency division multiplexing and time division multiplexing.
The programme demonstrates two methods of multiplexing used in the British telephone system - frequency division multiplexing and time division multiplexing.
| Module code and title: | T321, Telecommunication systems |
|---|---|
| Item code: | T321; 03 |
| First transmission date: | 13-03-1976 |
| Published: | 1976 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:22:20 |
| + Show more... | |
| Producer: | David Saunders |
| Contributors: | Glyn Martin; Ron McShane |
| Publisher: | BBC Open University |
| Keyword(s): | British telephone system; Frequency division multiplexing; Frequency loss; Pulse code modulation; Regenerator; Single sideband modulation; Time division multiplexing |
| Footage description: | Glyn Martin introduces the programme. Ron McShane, at the G.P.O. Technical Training Centre, Stone, uses the equipment there to demonstrate the build up of 12 separate telephone channels to form a frequency division multiplexed basic group. Glyn Martin joins in. McShane goes on to demonstrate the formation of a super group of multiplexed signals at a frequency range between 312kHz- and 552kHz. Glyn Martin, with animations, summarises how an F.D.M. system is built up. Ron McShane discusses the characteristics of a 4mHz_ coaxial transmission line. The attenuation frequency response of a 2km length of cable is displayed on the spectrum analyser. Glyn Martin joins in. Glyn Martin briefly introduces the sequence on Time Division Multiplexing. Ron McShane, with an oscilloscope, explains how the signal is sampled in this system. McShane goes on to explain and demonstrate how signals are pulse coded and then transmitted on one channel of a 24 channel system. Martin explains why synchronisation is necessary and how this is provided by alternate digit inversion. An animation helps make the points. Ron McShane explains what alternate mark conversion is and how it is achieved. He examines the spectrum of these pulses. Glyn Martin and Ron McShane explain and demonstrate the need for regenerators every 2km along a transmission line to provide amplification and synchronisation. The effect on a signal of too great a distance between regenerators is also demonstrated. |
| Master spool number: | 6HT/71989 |
| Production number: | 6HT71989 |
| Videofinder number: | 1344 |
| Available to public: | no |
