Browse Prior Art Database

Loop Off Line Detector

IP.com Disclosure Number: IPCOM000110111D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 81K

Publishing Venue

IBM

Related People

Hagiwara, K: AUTHOR [+3]

Abstract

Disclosed is a technique wherein loop communication is automatically recovered upon cabling failure except for a failure on the main loop by using a loop offline detector.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 60% of the total text.

Loop Off Line Detector

       Disclosed is a technique wherein loop communication is
automatically recovered upon cabling failure except for a failure on
the main loop by using a loop offline detector.

      Loop communication protocol is widely used to connect a large
number of terminals to a host computer because the cost of cabling is
relatively low.  However, this protocol has a weak point in that all
communications are interrupted when cabling failure occurs.  By using
loop offline detector, loop communication is automatically recovered
upon cabling failure except a failure on main loop.

      In Fig. 1, loop offline detectors are connected in the main
loop.  Terminal devices are connected in a sub-loop to one of the
loop offline detectors.  Loop signals from the controller go through
the loop offline detector 1, sub-loop 1 and come back to loop offline
detector 1 and then to offline detector 2 and to sub-loop 2, and so
on, until signals come back to the controller.  The loop offline
detector monitors poll signal from main loop and beacon signal from
sub-loop, respectively.  When cabling in the sub-loop fails for some
reason, a beacon signal is generated by the terminal which detected
the cabling failure.

      Functionally, the loop offline detector is normally in
pass-through mode in which signals on the main loop passes through
loop offline detector to associated sub-loop and back to the loop
offline detector where the signals propagate dow...