During the transmission of a signal, attenuation occurs and noise is picked up.

1. (a)State what is meant by:
2. (a)(i)attenuation[1]
3. (a)(ii)noise.[2]
4. (b)By reference to (a)(ii), explain the advantage of the transmission of the signal in digital form rather than in analogue form.[1]
5. (c)Part of an analogue signal is shown in Fig. 4.1. [Figure 4.1] The signal is to be transmitted in digital form. The analogue signal is sampled at a frequency of 1.0 × 103Hz using an analogue-to-digital converter (ADC). The ADC produces 4-bit numbers. The times t at which the analogue signal is sampled are shown in Fig. 4.2. [Figure 4.2] On Fig. 4.2:
6. (c)(i)for the digital number at time t = 3.0 ms, underline the least significant bit (LSB)[1]
7. (c)(ii)state the digital numbers corresponding to the sampling times between time t = 4.0ms and time t = 6.0 ms.[2]
8. (d)The transmitted digital signal is converted back to an analogue signal using a digital-to- analogue converter (DAC). On Fig. 4.3, show the variation with time t of the output levels of the DAC for time t = 0 to time t = 4.0 ms. Assume that there is negligible time delay in the transmission line. [Figure 4.3][3]

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