Telecommunications Weighting Filters

CCITT and C-message weighting filters are bandpass filters used to measure audio-frequency noise on telephone circuits. The CCITT (ITU-T) filter is used for international telephone circuits. The C-message filter is typically used for North American telephone circuits.

The frequency response of the CCITT and C-message weighting filters are specified in the ITU-T O.41 standard and Bell System Technical Reference 41009, respectively. The following figure shows the relative attenuation defined for the CCITT and C-message weighting filters.

Figure 24. Relative Attenuation of CCITT and C-message Weighting Filters

1378