(a(i))[1]
Explain what the term noise means.
(a(ii))[1]
Explain what the term attenuation means.
(b(i))[4]
A microphone is linked to a receiver by a wire pair, as shown in Fig. 11.1. The attenuation per unit length of the wire pair is $12\,\text{dB km}^{-1}$. The noise power in the wire pair is $3.4 \times 10^{-9}\,\text{W}$. The microphone emits a signal power of $2.9\,\mu\text{W}$. Calculate the maximum length of the wire pair for which the minimum signal-to-noise ratio is $24\,\text{dB}$.
(b(ii))[2]
Communication is needed over a distance greater than the value found in (i). Suggest how the circuit of Fig. 11.1 could be changed so that the minimum signal-to-noise ratio at the receiver is not lowered.
(b)
A microphone is linked to a receiver by a wire pair, as shown in Fig. 11.1.