Study figure 5-6 again and follow the pollingsequence of the four units in the net. The last reporton the top line is an NCS report and call to PU 04.This is followed by PU 04’s response on the left sideof line two. Next, PU 56 is called and responds witha picket reply. Upon completion of PU 56’s reply, PU64 is called. After 15 frame times without a response,PU 64 is called again. PU 64 appears to haveresponded to the second call, but the LMS-11 onlyrecognized the five preamble frames.By using the link monitor display, the operator ortechnician can make sure the connectivity has beenestablished and that all the correct PUs are beingpolled and are responding.Figure 5-6 also shows several problems thatcommonly occur during Link-11 operations. Noticethat PU 64 sometimes responds to the first call-up,sometimes to the second call-up, and sometimes PU64 does not respond at all. PU 56 responds all thetime except for the call-up at the end of line two andbeginning of line three. On line six there is a doubleresponse, or echo, from PU 04. If you were toexamine this particular sequence using the frame-by-frame analysis, you would find the PU 04 was calledagain. This indicates the NCS did not receive thereport from PU 04 and repeated the call-up during themiddle of the response.Figure 5-8.—Link-11 messages as displayed by theLMS-11 link monitor mode.Status DisplayAs shown in figure 5-9, the status display is at thebottom of each of the LMS-11 display screens. Thestatus display consists of the status box and two linesof information just above the status box. The top line,with the heading “XMT-ADDRS:” displays theaddresses of all PUs in the order they are being polled.The operator can monitor the polling in real time. Thedisplayed addresses change colors to indicate theirstatus. If the address is yellow, it is currently beinginterrogated. The yellow address turns green whenthe start code is received. The yellow address turnsred when the PU has been interrogated twice and noresponse is received.The line under the “XMT-ADDRS:” is used todisplay system messages and LMS-11 alerts. Alertsare displayed on the left side of this line. Systemmessages are displayed on the right side of the line.The status box provides the operator withinformation about signal processing, link activity, and ,raw recording of link data. Just below each of theframe types, a small green box, or light, appears toindicate the type of frame being processed. Thesesignal processing status indicators are not displayed inreal time. They are updated approximately every 50milliseconds. The signal processing indicators are asfollows:Figure 5-7.—The link monitor display pattern.5-11
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
