1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 - TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU-!).4%.!.#% G0G0).42/$5#4)/.!.$G0G0%.%2!,G0G002).#)0,%302).#)0,%3G0G0b) Deferred maintenance alarm (DMA);c) Maintenance event information (MEI).Definitions of PMA, DMA and MEI are found in Recommendation M.20
2、, 5.4.1.3 Guidance for using alarm information3.1 HierarchyThe alarm information from transmission systems and equipment is based on a hierarchy of:a) alarms and indications displayed on failed equipment or systems,b) office audible/visual alarms which alert local staff, andc) remote information whi
3、ch appears on a display monitored by centralized maintenance staff which is notcollocated with the failed equipment or systems.This alarm hierarchy is used in failure localization, either for a maintenance entity, or for specific equipmentwithin a maintenance entity.3.2 DisplayAlarm information can
4、be displayed to help in localization in different ways, such as:a) locally on the equipment,b) on site in the same building as the equipment, orc) remotely at a building not collocated with the equipment.Both localized and on-site displays are used by on-site maintenance staff. Remote displays are n
5、ormally usedeither for coverage during periods when a building is not staffed or to obtain a wider maintenance perspective from asingle location on a possibly large number of systems.2 Fascicle IV.1 - Rec. M.32For example, the remote maintenance strategy of 3.5 can be used first to localize a troubl
6、e to a maintenanceentity. Then, maintenance staff can obtain further remote (or otherwise made available) information to localize thefailure to specific equipment. After this, the maintenance staff can use the local alarm maintenance strategy of 3.7 toisolate and correct the failure.3.3 Consideratio
7、ns for local or remote alarm monitoringAlarm information may be displayed locally on equipment, or on-site in the same building as the monitoredequipment using external monitoring equipment. Use of such displays implies that maintenance staff must be present orvisit the site to observe the informati
8、on.Remote alarm monitoring provides a means for staff at a centralized location, not collocated with thetransmission systems and equipment, to monitor them.The choice between local and remote monitoring and the degree of centralization and automation employeddepends on a number of factors, including
9、 the type of maintenance organization, the expected failure rates and thephysical locations involved.3.4 Reducing unnecessary maintenance activityWhen an equipment failure requiring some maintenance activity occurs, alarms should, if possible, begenerated by the maintenance entity of which the equip
10、ment is part. The general rule is that maintenance activitiesshould be directed only at the maintenance entity in which the failure exists. Thus, techniques should be used whichprevent unwanted alarms (and the resulting unnecessary maintenance activity) beyond the maintenance entity in whicha failur
11、e exists. Also, maintenance entities downstream of the failed maintenance entity should have a means ofrecognizing that a failure has occurred upstream, as part of the aim of reducing maintenance activity. Provision may bemade at a maintenance entity to indicate an upstream failure and/or inhibit un
12、necessary actions. For example, in digitaltransmission systems and equipment, this may be accomplished by the use of: alarm indication signal (AIS); service alarm (SA); upstream failure indication (UFI).For definition of AIS, SA and UFI see Recommendation M.20, 5.4.2.3.5 Considerations for remote ma
13、intenance alarm informationRemote maintenance alarm information provides a means for staff not collocated with transmission systemsand equipment to nonetheless monitor and control them. The monitored equipment may be located in unstaffedlocations. This section recommends the principles which should
14、be followed if remote alarm information is provided.3.5.1 Identification and localization are required to determine what the response should be: start restoration ofservice by using alternate routes, dispatch for maintenance of failed equipment, or wait and gather further informationto better identi
15、fy the nature and/or seriousness of the problem.3.5.2 The decision to send maintenance staff is based upon the maintenance philosophy in Recommendation M.20, 1.1.3.6 Maintenance alarm arrangementsMaintenance alarm arrangements are based on the use of audible/visual alarm systems. These systemsprovid
16、e alarms which direct on-site staff to the location of the failed equipment. The objective when providingaudible/visual alarm indications is that they should permit on-site maintenance staff to detect and locate the source offailure in a timely fashion in line with other priorities. Note that distin
17、ctive sounds may be used to differentiate audiblealarms. Also, visual signals should be able to direct maintenance staff to the failed equipment or to a point where thelocation of the failure can be determined.Fascicle IV.1 - Rec. M.32 33.7 Use of local alarm information3.7.1 Local alarm information
18、 is concerned with alerting on-site maintenance staff to equipment failures. The localmaintenance activities usually entail the location and correction of the failure. To carry this out effectively andefficiently, information which helps direct the maintenance staff to the failure should be provided
19、 directly from thefailed equipment.3.7.2 Local alarm information is derived from local failure indications, together with the maintenance staff use oftests and relevant documentation. This should be sufficient to localize the failure within the failed equipment.3.7.3 Note that a further purpose of l
20、ocal failure indications is to provide a backup for remote indications, in theevent that there is a failure in communications between monitored equipment and a central monitoring location.4 General considerations4.1 MonitoringIn general, failures of equipment should be detected by continuous (or nea
21、rly continuous) automaticmonitoring, as opposed to monitoring or testing involving human intervention. Note that shared, but automatic,monitoring is considered nearly continuous. Continuous (or nearly continuous) monitoring is often made feasible byvirtue of advances in technology, and by virtue of
22、the large number of circuits affected or jeopardized by atransmission system failure. In addition, continuous (or nearly continuous) monitoring is faster, more reliable, and lesslabor intensive than alternative monitoring strategies.4.2 Uses of PMA, DMA and MEI4.2.1 When reporting or displaying alar
23、ms either locally or remotely, it is important to distinguish betweenPMA/DMA indications and MEI indications. PMA/DMA indications are those which cause maintenance staff to bealerted (e.g., by ringing a bell), and MEI indications are those which are displayed in response to staff interrogations orin
24、 conjunction with other indications (e.g., alarms) which are spontaneously generated.4.2.2 These distinctions should be defined for each transmission system and equipment in order for alarmindications to be properly processed. These distinctions may be of particular importance when using remote alar
25、msurveillance systems, where large numbers of PMA, DMA and MEI indications must be dealt with by maintenancestaff.4.2.3 MEI indications may be used as aids in failure localization or verification of remote operations (such asremote control of protection switching) under manual control. The informati
26、on conveyed by MEI indications may alsobe used to supplement that convoyed by PMA/DMA indications.4.2.4 Note that detection of failures is accomplished by having suitable monitors associated with each maintenanceentity. The criteria for activating alarm indications at a maintenance entity should gen
27、erally be based on limits on themaintenance entities, which will generally be related to the performance objectives of the transmission systems.4.2.5 To aid in the dispatch of personnel, remote indications should include the following information:a) identification of the failed transmission system o
28、r equipment and nature of trouble condition,b) distinction between service-affecting failures and non- service-affecting failures where such a distinctionis possible, andc) severity of the failure which has occurred.4.3 Transmission and presentation of alarm information4.3.1 There are two basic inte
29、rface arrangements for transferring alarm information between monitored andmonitoring equipment:a) discrete, parallel, andb) serial data.4 Fascicle IV.1 - Rec. M.32The parallel method of data gathering and control uses discrete wires for implementing each function. Theserial data method of gathering
30、 and control uses a single pair of wires to carry serial (in time) data points, rather thanindividual wires for each point. Much new telecommunications equipment is “intelligent”, that is, it employsmicroprocessor circuit design, which lends itself more readily to serial data transfer rather than to
31、 parallel.4.3.2 The presentation of alarm information can be:a) visual (lamp, LED, printer or display indication), and/orb) audible (bell, tones or voice).The alarm information may be presented as:a) an indication at an alarm interface (e.g., contact function, d.c. signal) and/orb) an alarm message
32、on the man-machine interface.This alarm message may contain:i) heading (name of maintenance entity, date, time, etc.),ii) category of failure (PMA, DMA, MEI),iii) description of failure, which may include the cause of failure, location of the failed item(s) and otherinformation which can be useful i
33、n locating the failed item(s),iv) possible consequences of the failure, andv) automatic actions performed by the network (internal protection and service actions).4.4 Possible use of MEIsAdministrations using MEI may desire to alert maintenance staff by means of a PMA or DMA. The criteriaand arrange
34、ments1)for generating PMA or DMA based on analysis of MEI are left to their discretion.4.5 Considerations for protection switching and controlTo meet transmission system availability objectives or maintenance criteria, transmission systems may beprovided with protection equipment. Such equipment, if
35、 provided, may have the following capabilities:a) automatic protection switching of service from failed regular equipment to working standby equipment,b) automatic protection switching of service to overcome transmission degradation caused, for example, byradio path fading,c) remotely controlled pro
36、tection switching of service between regular equipment and standby equipment,and/ord) locally controlled protection switching of service between regular equipment and standby equipment._1)The arrangements to generate such information may take place in the transmission system or in auxiliary supervision systems.
