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