Browse Prior Art Database

Technique For Prevention of Wandering Beacon Signal in Loop System

IP.com Disclosure Number: IPCOM000048651D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hughes, DR: AUTHOR [+2]

Abstract

This article describes a technique for deducing the effect of upstream data on a beacon signal generated by a loop terminal when contact with the loop primary controller has been lost.

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This is the abbreviated version, containing approximately 71% of the total text.

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Technique For Prevention of Wandering Beacon Signal in Loop System

This article describes a technique for deducing the effect of upstream data on a beacon signal generated by a loop terminal when contact with the loop primary controller has been lost.

To improve the availability of a loop for message transmission, each terminal on the loop maintains a time-out operation. The time-out is restarted whenever a flag character is received. If a time out is completed, the terminal assumes contact with the loop controller has been lost and initiates the transmission of beacon messages. The terminal concurrently searches the inbound line for a flag character and, upon detecting one, ceases to transmit beacon messages.

Theoretically, when all terminals except one have ceased to transmit beacon messages, the failure causing the time-out condition is isolated either to the terminal sending the beacon message, the next terminal upstream, or the loop cable connecting the two terminals.

Loss of contact between terminals and the loop controller can be caused by a number of different types of malfunctions, some of which will cause a random data pattern which will look like a flag character to a terminal. As a result, terminals on the loop may temporarily cease to transmit beacon signals even though contact with the loop controller has not actually been re-established.

When the transmit clock of the terminal in a beacon condition is continuously corrected by synchronizing on rece...