Data transmission Flashcards
What do infrared signals do?
Infrared signals carry information that allows electronic and electrical devices to be controlled.
How does a TV remote work?
- Pressing a button on the remote control device completes the circuit. A coded signal is sent to a light emitting diode or LED at the front of the remote.
- The signal includes a start command, the instruction command, a device code and a stop command.
- The LED transmits the series of pulses. This is received by the device and decoded to allow the television to change channel or volume.
When did the digital switchover start and when will it end?
The switchover from analogue to digital started in 2009 and is planned to finish by 2015. This may be delayed until more people buy digital radios.
The switchover for both radio and TV means:
- Improved signal quality for both picture and sound
- A greater choice of programmes
- Being able to interact with the programme
- Information services such as programme guides and subtitles.
What do optical fibres do?
Optical fibres allow data to be transmitted very quickly using pulses of light.
An optical fibre is
solid, not a hollow.
How is an anologue signal sent?
- Before an analogue signal is transmitted, it is added to a carrier wave.
- The frequency of the carrier wave is usually higher.
- The combined wave is transmitted.
- Interference from another wave can also be added and transmitted.
- If the wave is amplified, the interference is amplified as well.
Is there interference in digital signals?
Interference also occurs on digital signals, but is not apparent because the digital signal only has two values.
What does multiplexing allow.
Multiplexing allows a large number of digital signals to be transmitted at the same time.
