An analogue signal is to be transmitted to a receiver. Before transmission, the signal passes through an analogue-to-digital converter (ADC). After transmission it passes through a digital-to-analogue converter (DAC) before finally reaching the receiver, as shown in [Figure 5.1].

1. (a)State two advantages of converting the signal into digital form for transmission.[2]
2. (b)(i)The variation with time of the potential difference (p.d.) of the input signal is shown in [Figure 5.2]. The ADC has a sampling frequency of 250 Hz and uses 4-bit sampling, with the least significant bit corresponding to 1 mV. The signal is first sampled at time 0, when the sampled bits are 0001. State the sampled bits at time 4ms and time 8 ms.[1]
3. (b)(ii)Part of the signal received by the receiver, after the sampled signal has passed through the DAC, is shown in [Figure 5.3]. On [Figure 5.3], complete the line to show the received signal for time 0 to time 12ms.[2]
4. (c)The ADC in (b) is replaced with one that has a sampling frequency of 500Hz and uses 3-bit sampling, with the least significant bit corresponding to 2mV. On [Figure 5.4], sketch the signal that is now received, after passing through the DAC, from time 0 to time 12 ms.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.