Data Transmission

Data Transmission

1. Digital Signals

   • Infrared signals carry information that allows electronic and electrical devices to be controlled.
   • Pressing button on controls completes circuit.
     • Coded signal is sent to light emitting diode or LED at front of remote.
   • Signal includes start, instruction, device code and stop demands.
   • LED transmits series of pulses. Received by device and decoded to allow TV to change channel or volume.
   • Switch over from digital to analogue started in 2009.
     • Improved signal quality for picture and sound.
     • Greater choice of programmes.
     • Able to interact with programme.
     • Information services available.

2. Optical Fibres

   • Data to be transmitted quickly using pulses of light.
   • Solid not hollow tube.

3. Advantages of Digital Signals

   • Before analogue signal transmitted, it is added to a carrier wave.
     • Frequency of carrier wave is usually high.
   • The combined wave is transmitted.
   • Interference from other waves can also be added and transmitted.
   • If wave is amplified, so it the interference.
   • Interference also occurs on digital signals but is not apparent because digital signal only has 2 values.
   • Multiplexing allows a large number of digital signals to be transmitted at the same time.