Nortel DMS-100 External Devices Maintenance Overview |
Functional Description
The External Devices (EXT) subsystem performs the following basic functions:
The EXT subsystem is one of the subsystems in the DMS-100 family maintenance system. Each of these subsystems controls its alarm status display in the system status area of the EXT Maintenance and Administration Position (MAP) level display. Figure 1 shows the EXT level MAP display. The alarm system software checks for changes in the alarm status of the subsystems and updates the related audible and visual alarm indicators. These checks and updates occur about every five seconds. The EXT subsystem reports alarms that other maintenance subsystems do not report.

Figure 1 - EXT Level MAP Display
The EXT subsystem does not participate in call processing. The EXT subsystem monitors the alarm status of other subsystems. This monitoring helps to ensure proper the operation of DMS-100 family switches, so call processing can function properly.
Office Alarm System
The Office Alarm System (OAS) consists of the following:
The standby OAU is also called the standby MTM or standby ISM.
Office Alarm System Versions
The following OAS versions exist:
For detailed information on alarm system versions, refer to DMS-100 Family Alarm System Description, NTP 297-1001-122.
Alarm Detection and Reporting
The alarm system software monitors and controls alarm system hardware. When the alarm system software receives alarm or control inputs, it operates or releases Signal Distribution (SD) points in the alarm system hardware. The operation or release of SD points activates or deactivates audible or visual alarm or control functions.
Alarm and control inputs monitored by alarm system hardware connect to the alarm system software through Scan (SC) points. SC points detect signals generated by the following:
Scan points have related SD points. The software that monitors the SC points is part of the EXT subsystem. The descriptions of data schema tables ALMSCGRP (Alarm Scan Group), ALMSC (Alarm Scan), ALMSDGRP (Alarm Signal Distributor Group), and ALMSD (Alarm Signal Distributor Point) in Translations Guide describe SC and SD point assignments for the OAS.
Alarm System Hardware
The following sections describe OAS hardware and the frame and cabinet shelves OAS hardware is provisioned on. For detailed information on alarm system hardware, see DMS-100 Family Alarm System Description, NTP 297-1001-122.
Office Alarm Unit
The Office Alarm Unit (OAU) is a MTM, STM (compact MTM), or ISM shelf equipped with a transmission, a processor, a control, and a power converter card. The OAU also has slots for up to 12 office alarm circuit, signal distribution, and scan detector cards.
The primary and standby OAUs connect to each other through the following:
The alarm crosspoint field shelf and AXU also connect the primary and standby OAUs to other components of the OAS. Figure 2 shows the major hardware components of the OAS and their shelf locations (in inches from the floor).

Figure 2 - Alarm System Hardware
Maintenance Trunk Module
The maintenance trunk module is a Peripheral Module (PM) that can contain an OAU or a standby MTM. For detailed information on the MTM, see Peripheral Modules Maintenance Guide, NTP 297-1001-592.
Service Trunk Module
The service trunk module is a PM that consists of two compact MTM. The STM can contain an OAU or a standby MTM. For detailed information on the STM, see Peripheral Modules Maintenance Guide, NTP 297-1001-592.
Integrated Services Module
The integrated services module is a single shelf that replaces the Trunk Module (TM) or the Maintenance Trunk Module (MTM) shelf. The ISM shelf mounts on the Cabinetized ISM (CISM) or the Frame ISM (ISME). For detailed information on the ISM, see Peripheral Modules Maintenance Guide, 297-1001-592.
Alarms
For detailed information on alarms and alarm circuits, see DMS-100 Family Alarm System Description, NTP 297-1001-122.
Alarm Conditions
The EXT subsystem detects the following types of alarm conditions:
Power Faults
Power faults are the most severe alarm conditions detected by the EXT subsystem. A power interruption can affect the operation of individual frames or an entire switch. The power faults indicated at the EXT level of the MAP display are as follows:
Frame Supervisory Panels Faults
One or more of the following alarm conditions generates a FSP alarm:
The PDCFAIL and ABSFAIL alarms also generate a FSP alarm. The FSP alarm SC point identifies the aisle where the failure occurred and the PDCFAIL or ABSFAIL SC point indicates the nature (for example, a blown fuse) and location (for example, the PDC) of the alarm condition.
A blown fuse or power converter failure on a frame that contains a subsystem (for example, a TM) also generates an alarm for the affected subsystem. The EXT subsystem generates another alarm: the FSP alarm. If a FSP alarm occurs at the same time as an alarm in another subsystem, the probable cause is a local power failure.
The No Alarm (NoAlm) condition in the EXT MAP level alarm display indicates a SC point change that does not require an alarm. The system-level MAP display does not identify NoAlm conditions.
The NoAlm SC points are part of the operational hardware of the alarm system. These SC points, with the exception of TSTSCAN, monitor manual control switches in the alarm system hardware. When one of these SC points changes state, the alarm system software performs the required control function (for example, activates remote alarm transfer). The external alarms status displays these SC points generate can provide information on the status of the alarm system manual controls at remote locations. You can use these reports to check the operation of the alarm system manual controls.
System-Detected Alarm Conditions
Alarm system hardware or software problems can cause system-detected alarm conditions. When a system-detected alarm condition occurs, the switch remains operational, but the OAS may not report alarms properly. The most severe system-detected alarm condition in the EXT subsystem is an Automated Message Accounting (AMA) failure.
Alarm battery failures can cause major system-detected alarm condtions. Examples of this type of fault are the following:
Miscellaneous Alarm Conditions
Operating company personnel can program the alarm system to monitor conditions such as office temperature and humidity. Though these conditions rarely affect switch functions, you can assign any level of alarm severity from critical to no alarm. Conditions such as high temperature and humidity are called miscellaneous alarm conditions.
The operating company assigns SC points to miscellaneous alarms. Table ALMSC contains datafill for the function and alarm severity of each miscellaneous alarm SC point. For a list of suggested functions for miscellaneous alarm SC points and a description of the assignment of SC points to office alarm circuits, refer to the description of table ALMSC in Translations Guide.
The number of SC points available for assignment to miscellaneous alarms is site dependent.
Emergency Service Alarms
The emergency service alarms are as follows:
When you make an emergency call to the Fire and Police Trunk (FPT), the system generates the ESR minor alarm. The system also generates an ESR100 log.
When the system routes an emergency call to the FPT trunk, but the attendant does not answer within 30 seconds, the alarm system generates the ESR_TIME minor alarm.
The operating company can control whether or not an emergencey service alarm condition generates an alarm at the MAP terminal. To deactivate the generation an alarm, perform the following procedure.
At the MAP terminal:
1. To access table SFWALARM (Software Alarm), type:
>TABLE SFWALARM
2. To position on the alarm tuple, type:
>POS ESR_ALARM
3. Type:
>CHA
4. To change the tuple, type:
>Y
5. To enter No Alarm, type:
>N
6. To end the field, type:
>$
To activate the generation of an alarm, enter Y at Step 5 of the above procedure.
Escalation to Manual Maintenance
The EXT subsystem collects alarms from a variety of external devices and other subsystems that make up the DMS-100 family switch. When the EXT subsystem reports software alarms at the MAP terminal, the system has failed to correct the problems indicated by these alarms. In this case, operating company personnel must manually intervene to return faulty hardware to normal operation.
Although the DMS-100 family switches are designed to operate with minimum manual intervention, some manual maintenance is required. MAP responses and log reports indicate the type of manual maintenance required.