US 6,477,249 B1Granted

Communications signal splitter and filter

AssigneeNortel Networks Limited

InventorsRoger James Williamson, Leslie Derek Humphrey

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Abstract

A splitter separates telephony traffic (POTS) from digital subscriber line (ADSL) traffic occupying a higher frequency band. The splitter comprises a low-pass filter for passing the telephony traffic, the low-pass filter being operable to vary its filtering response between a first low-pass response for use during telephony speech traffic, and a second, more restrictive, low-pass response for use during at least part of the time that telephony signalling traffic is present. During speech traffic a filter is used which provides a good impedance match with a telephony terminal or linecard so as to minimize detrimental effects on sidetone and echo performance which may impair a user's speech quality. The filter response can be varied according to a detected property of the telephony traffic, such as amplitude or rate of change of amplitude of the traffic.

Claims17

Dependent claims

A splitter for separating telephony traffic from further traffic occupying a higher frequency band, the telephony traffic comprising speech and signalling traffic, the splitter device comprising:

an input for transmitting and receiving the telephony and the further traffic;
a detector for detecting a property characteristic of the telephony traffic;
a high-pass filter coupled to the input for passing the further traffic;
and,
a low-pass filter coupled to the input for passing the telephony traffic, the low-pass filter being arranged so as to vary its filtering response between:
a first low-pass response for use during telephony speech traffic;
and,
a second, reduced cut-off frequency, low-pass response for use during at least a portion of the time that telephony signalling traffic is present;
and wherein the filter response is varied according to the property characteristic of the telephony traffic, said property being selected from the group consisting of, amplitude of the telephony traffic, rate of change of amplitude of the telephony traffic, and frequency content of the telephony traffic.

6 more elements

Dependencies are inferred from the claim text.