Network Impairments

• The transformers cannot pass DC and there is high harmonic distortion at low frequencies. Spectral shaping must be used to avoid 0-200 hz (approx).

• The codec filter rolls off from -3dB at 3400 hz to -14dB at 4000 hz. Equalization is used to correct.

• Robbed bit signaling (when used) steals the low order bit of every 6th sample.

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