Using Shannon's law, that the maximum data rate for a standard analog telephone line is approximately 30,000 bps with a signal-to-noise ratio of 30dB. The ratio of signal to noise is 1000, because the signal-to-noise ratio is 10 log10 signal dB / noise dB, as explained in Section 11.6.1.
If a binary signal is sent over a 10Khz channel whose signal-to-noise ratio is 20dB, what is the maximum achievable data rate?