Patent ID: 6757377
Filing Date: 2004-06-29
Classification: H04L

Abstract:
A filter system for connecting between a central office telephone switch and a telephone connection that can communicate voice and digital data channels using signals communicated between a central office and a customer premises, the system for suppressing transients and harmonics on the connection caused by a ring signal generated by the telephone switch in order to minimize adverse effects on the digital data channel on the connection, said ring signal composed of an on period and an off period, the filter system comprising:a first filter designed to implement a first low pass filter function to attenuate frequencies higher than said ring signal; a second filter designed to implement a second low pass filter function to attenuate frequencies higher than a voice channel; and a filter selector designed to impose said first filter on said signals whenever a telephone connected to said telephone connection is on-hook and said ring signal is present, and to impose said second filter on said signals whenever said telephone is off-hook and when said telephone is on-hook and said ring signal is absent, where the filter selector is line-powered, and where said first low pass filter function is applied for the duration of said on period of said ring signal.