1. Sound wave is an analogue signal.      Digital signal can only be 1s or 0s.      Analogue signal can have an infinite number of values between any two values.      External interference affects analogue signals but not digital signals.      When several signals are send along the same line at the same time, they are sorted out at the      receiving end by a demultiplexer.  2. The two advantages other than cost of using digital signals not analogue for transmission      of data are: More information can be transmitted with digital signals. Unlike analogue signals, any interference to the digital signals during transmission can be removed.