(a(i))[1]
State the meaning of attenuation.
(a(ii))[2]
State the meaning of noise.
(b(i))[3]
Fig. 5.1 shows the first part of the transmission line for a signal from a telephone exchange. At the exchange, the input signal to the transmission line has a power of $2.5 \times 10^{-3}\ \text{W}$. After the signal has moved $52\ \text{km}$ along the transmission line, its power is $7.8 \times 10^{-16}\ \text{W}$. The signal is then amplified. Calculate the attenuation per unit length, in $\text{dB km}^{-1}$, in the transmission line.
(b(ii))[2]
The amplifier has a gain of $115\ \text{dB}$. Calculate the signal power at the output of the amplifier.