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What are 833 and 899 alarms on a Dialogic?? DMG1000 Media Gateway?

Summary:
Description of what the 833 and 899 alarms mean on the Dialogic® DMG1000 Media Gateway Series model DMG1008LS, and what can cause the alarms to occur. 

Introduction

During normal use, the Dialogic® DMG1000 Media Gateway model DMG1008LS can register 833 (TDM Out of Service) and/or 899 (TDM In Service) alarms. These alarms do not appear to affect calls, but their source is unknown.

Explanation

The analog interface of the Dialogic® DMG1008LS gateway will register an 833 alarm when the voltage on the line drops below 2.0 volts. It will then register an 899 alarm when the voltage returns to a value above 4.4 volts.

Details

These alarms have been observed for gateways that are connected to large central office type PBX on premise (i.e.: SL100, DMS100) as well as for those connected directly to the central office (CO) in Centrex type installations. The times between the 833 and 899 alarms were short (generally 2-3 seconds) and the lines came back into service at the end of the test. The line indicators on the front of the gateway cycle from green (indicating good health) to red (indicating loss of loop) and then back again to green during the test.

Working with the PBX administrator or the line provider to disable the periodic port tests has been effective in stopping the alarms.

Please note that disabling these tests can hamper your line provider’s ability to proactively spot potential problems, so unless the alarms are bothersome you may want to consider just making note of them. However, if a line raises an 833 alarm and never raises a corresponding 899 alarm, that indicates the line is out of service, which also is indicated by a steady red-colored line indicator on the front of the gateway for each line that is in a perpetual out of service state.