METHOD AND DEVICE FOR DETECTING DUAL TONE ALARM SIGNAL IN TELEPHONE SYSTEM

Title:

METHOD AND DEVICE FOR DETECTING DUAL TONE ALARM SIGNAL IN TELEPHONE SYSTEM

Document Type and Number:

Japanese Patent JP3779874

Kind Code:

B2

Abstract:

PROBLEM TO BE SOLVED: To provide a device that provides an enhanced talk-down and talk-off immunity.
SOLUTION: The dual tone alarm signal detection device in a telephone system where at least an off-hook mode is available includes processing channels 104, 106 for each tone. Each channel consists of a band split filter 108 that extracts an object tone and attenuates other tone, a comparator 130 that compares an output of the band split filter with a threshold value, and an adaptive threshold generator 112 that generates the threshold value to be adapted to an output amplitude of the band split filter in order to eliminate voice and music imitation.

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Inventors:

Philip Chin

Application Number:

JP2000376279A

Publication Date:

May 31, 2006

Filing Date:

December 11, 2000

Export Citation:

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Assignee:

Zarlink Semiconductor, Inc.

International Classes:

H04L27/26; H04M1/00; H03L7/085; H03L7/099; H03L7/14; H03L7/18; H04J3/06; H04M1/02; H03L7/095; H04L12/70; (IPC1-7): H04M1/00; H04L27/26; H04M1/02

Domestic Patent References:

JP9307624A

Attorney, Agent or Firm:

Kensuke Isshiki
Noritaka Harashima
Satoshi Suzuki

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