The signal from a microphone is to be transmitted in digital form. A block diagram of part of the transmission system is shown in the figure below.
Suggest two advantages of the transmission of a signal in digital form rather than in analogue form.
State the function of the parallel-to-serial converter.
In a particular telephone system, the sampling frequency is 
. In the manufacture of a compact disc, the sampling frequency is approximately 
. Suggest and explain why the sampling frequency is much higher for the compact disc.
