The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 24, 2002
Filed:
Sep. 28, 1998
William G. Bartholomay, Orange, CT (US);
Santanu Bhattacharya, Delhi, IN;
Pushkal Yadav, New Delhi, IN;
Balaraj Vishnu Varthanan, Tamil Nadu, IN;
Transwitch Corporation, Shelton, CT (US);
Abstract
A method and apparatus for reliably detecting both AIS and AIS-CI signals in the presence of a bit error ratio up to 1×10 includes an AIS detector having an AIS indication output, a CI detector having a CI indication output, and a two signal AND gate having its inputs coupled to the respective outputs of the detectors and having an output indicative of an AIS-CI detection. The AIS detector has an adjustable zero threshold and the CI detector has a threshold output coupled to the AIS detector for adjusting the zero threshold. According to the method of the invention, the AIS detector zero threshold is normally set at the normal threshold (1×10 ) but is reset to a higher threshold (e.g., 2×10 ) when the CI detector detects the presence of the CI code word. The AIS signal is detected in a normal way and the AIS-CI signal is detected only when the CI detector detects the presence of the CI code word AND the AIS detector detects the presence of the AIS signal using the higher zero threshold. According to a preferred embodiment, the zero threshold is raised if the CI detector detects two consecutive CI code words, but the CI indication output is indicated only of the CI detector detects eight CI code words in 40 ms. The zero threshold is returned to normal when the CI detector detects ten consecutive absences of the CI code word.