The digital transmission of speech may be represented using the block diagram in the figure below.
Part of the signal at point P on the figure above is shown in the graph below.
The analogue-to-digital converter (ADC) samples the signal at time intervals of 
. Each sample is converted into a four-bit number with the smallest bit representing 
. Use the graph below to determine the four-bit number produced by the ADC at time
The digital number is transmitted and then converted to an analogue form by the digital-toanalogue converter (DAC). Use data from the graph above to draw, on the axes of the graph below, the output level of the DAC for time 
to time 
. Assume that there is no time delay of the transmission of the signal between point P and the output of the DAC.
