Explain data rates in public switched telephone network.
Data rates in PSTNs: A voice channel in a public switched telephone network is band restricted with a nominal bandwidth of 3.1 kHz. A first-cut estimate of it can be acquired from Nyquist's theorem that applies to noiseless states and channels:
R = 2H log V bps
Where
R = maximum data rate
H = bandwidth of the channel
V = number of discrete levels in the signal