3Com AccessBuilder 500, User Manual

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Introduction 1-11
ISDN VOICE This LED indicator provides confirmation that a voice call is
in progress, or the handset is off the hook and a dial tone is present,
indicating that an ISDN network connection is available.
ALARM This LED indicator provides confirmation that a fault has been
detected on one of the configured ports. Typically this would indicate
that a serial link has gone down, or that a configured port does not
have a cable connected to it.
ALERT This LED indicator is application specific and lights to indicate that
while the system is operating normally, it has detected a change in state.
For example, where an ISDN backup circuit or any other on-demand
circuits have been brought into use.
The ALERT LED can be disabled using the management software, if
required. See the AccessBuilder ISDN Access Router Software Reference
guide for details.