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2.5 Analog and Digital Transmissions

datacontinuous (e.g., voice)discrete (e.g., text)
signalcontinuous electromagnetic waves
 -- -
Used mainly for transmitting data across a network.
sequence of voltage pulses
  --| --|
--  --
Used mainly internally within computers.
transmissiontransmission of analog signals without regards to their content (the data may be analog or binary). The signals become weaker (attenuated) with the distance. Amplifiers may be used to strengthen the signals, but as side effect they also boost the noise. This might not be a problem for analog data, such as voice, but is a problem for digital data. Transmission that is concerned with the content of the signal. Repeaters are used to overcome attenuation. A repeater recovers the digital pattern from the signal it gets, and resubmits a new signal.

Advantages of digital transmission.

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