This philtre was designed to maximise its response to the types of impulsive noise often coupled into audio cables as they pass through telephone switching facilities. The CCIR 468-curve peaks at 6.3 kHz, where it has 12 dB of gain (relative to 1 kHz). From here, it gently rolls off low frequencies at a 6 dB/octave rate, but it quickly attenuates high frequencies at ~30 dB/octave (it is down –22.5 dB at 20 kHz, relative to +12 dB at 6.3 kHz).