Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Transient Signal Detector for Modems

IP.com Disclosure Number: IPCOM000049582D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Godard, D: AUTHOR [+3]

Abstract

In data transmission, the beginning of a transmission has to be detected rapidly by the receiver. Generally speaking, when the transmission starts, at least carrier information is fed to the line, and therefore the receiver, detecting a transition from no information to carrier information occurring on the input line, should prepare itself for receiving messages. However, transient noise should not be mistaken for the beginning of transmission.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Transient Signal Detector for Modems

In data transmission, the beginning of a transmission has to be detected rapidly by the receiver. Generally speaking, when the transmission starts, at least carrier information is fed to the line, and therefore the receiver, detecting a transition from no information to carrier information occurring on the input line, should prepare itself for receiving messages. However, transient noise should not be mistaken for the beginning of transmission.

According to the V29 CCITT Recommendation, the beginning of transmission should include synchronizing signals consisting of a sequence of periodic alterations between two signal elements for a given period of time. These signal elements are selected to generate three tones within the receiver bandwidth. Two of these tones (F1 and F2) are at Nyquist frequencies, i.e. (see original), where F/c/ is the carrier frequency, T is the signalling period, and the third tone is the carrier itself.

A device is proposed here for detecting the beginning of a transmission based on the contents of the synchronizing sequence or, more precisely, based on a sequence including the said synchronizing sequence being eventually preceded with a very short repetition of preselected symbols, and followed by second preselected symbols breaking the period operation would be performed through the following operations: Filtering to reject the above-mentioned three tones,

integrating the filtered signal, and then

Differentiating the integrated signal to discriminate between

two transitions o...