Available online
Description
The programme demonstrates the principles of scanning used to form T.V. pictures. It shows some of the waveforms found in television systems and illustrates some systems defects.
The programme demonstrates the principles of scanning used to form T.V. pictures. It shows some of the waveforms found in television systems and illustrates some systems defects.
| Module code and title: | T321, Telecommunication systems |
|---|---|
| Item code: | T321; 11 |
| First transmission date: | 17-07-1976 |
| Published: | 1976 |
| Rights Statement: | |
| Restrictions on use: | |
| Duration: | 00:24:10 |
| + Show more... | |
| Producer: | David Saunders |
| Contributors: | Glyn Martin; G.(Gaby) Smol |
| Publisher: | BBC Open University |
| Keyword(s): | Eight-line raster; Electron beam; Horizontal split screen; Oscilloscope; Scanning; Scanning waveforms; Sychronising pulses; System defects; Television picture; Video signals |
| Footage description: | Gaby Smol introduces the programme. He demonstrates and explains the principles of scanning in television receivers. A simple eight line raster and saw tooth waveform are displayed on an oscilloscope. Smol goes on to improve the picture by increasing the number of lines to 256. Glyn Martin at the BBC Training Centre, Wood Norton, He points out some of the apparatus available for teaching. Martin uses an oscilloscope to demonstrate the field scanning waveforms of a television set. He then displays trigger pulses and explains why these are necessary to time the magnetic deflection coils in a t.v. monitor. Martin next displays pulses which trigger the line scan generator. Gaby Smol displays waveforms corresponding to the individual lines of a t.v. monitor. He uses split screen technique to show the waveform and picture at the same time. Glyn Martin, with an animated diagram, explains how the scanning system can be used to construct a horizontal split screen effect. He goes on to demonstrate on a monitor. Martin next uses an animated diagram to explain how waveforms of individual lines can be displayed. He goes on to demonstrate this on the monitor. Gaby Smol discusses and then demonstrates the effects of introducing defects into the transmission path of a video signal. He looks at waveforms reduced in the high frequency band and then in the low frequency band. These are shown on the monitor. The split screen facility shows both the reduced waveforms and their effect on the picture. Smol next looks at the effects of introducing non-linearities into the transmission channel. To demonstrate he displays a 'staircase' waveform on the monitor. He introduces non-linearity to the channel and the effect on the waveform can be seen. Smol, with an animated diagram, examines the effect of signal propogation along two paths of different length. He demonstrates the effect of this on a t.v. test card displayed on a monitor. Ghosting results. Glyn Martin, with a t.v. test card, demonstrates how it can be used to locate and correct different systems defects. The test card is displayed on a monitor and several defects are introduced to the picture. |
| Master spool number: | 6HT/71993 |
| Production number: | 00525_5230 |
| Videofinder number: | 1352 |
| Available to public: | no |
