Comtech EF Data CRS-200 REDUNDANCY SWITCH - Manual (Page 28)

CRS-200 COMTECH COMMUNICATIONS CORPORATION
CRS-200 REDUNDANCY SWITCH - OPERATIONS MANUAL PAGE 26
NOTE
Please read this Operations Manual in conjunction with the Operations
Manual for the CDM-500, CDM-550, or CDM-550T as details of the
operation of the Modem equipment is not covered in this document.
8.4 ADDITIONAL SWITCH CONFIGURATION
Once all IF cabling is complete, the system should be completely operational but still in
Manual mode. The user may choose to operate in this manner, but the switch will not
automatically react to traffic modem failures it detects. If the system is to be left unattended,
it is recommended that the user go to the “CONFIG, AUTO” menu and turn on Auto mode.
The Stored Event LED will stop blinking, and now the switch will force the redundant modem
to bridge, then back up the first activated modem which fails. Two other configuration
options are useful for fine tuning the switch’s Auto mode, and are described next.
8.5.1 HOLDOFFS
When in Auto mode, additional delays may be introduced to the backup procedure
by going to the “CONFIG, OPTIONS, HOLDOFFS” menu and changing the “backup
holdoff” from its default of 5 seconds to anywhere from 2 to 99 seconds. When a
traffic modem fails and the redundant modem is forced to “bridge” it, the switch waits
this length of time to determine two things: does the traffic modem remain faulted,
and is the redundant modem not exhibiting the same fault? If the answer to both
questions is “yes” for the entire holdoff time, the switch performs the actual backup.
The “restore holdoff”, which is also programmable from 2 to 99 seconds, determines
the switch’s ability to automatically put a backed up traffic modem online again if its
fault goes away. Normally, a failed modem that was taken offline will remain offline
indefinitely even in Auto mode unless another traffic modem fails. In this case, the
originally failed modem will be put back online by the switch if its fault has been
clear for the full programmed restore holdoff time. The redundant modem can then
be used to backup the newly failed modem. The switch has no prioritization scheme,
so that multiple traffic modem failures are treated on a ‘first come, first serve’ basis
only.
8.5.2 ALARM MASK
Another way to adjust the switch’s reaction in Auto mode is to mask modem faults.
Under “CONFIG, OPTIONS, ALARM-MASK, MODEM-ALARMS”, the user may
disable Tx, Rx or both faults from being seen by the switch. This not only prevents the
switch from taking automatic action, but also keeps the faults from being logged on
its stored events list. Note that these masks are global to all the modems attached to
the switch. Note also that each modem can be individually programmed with its own
set of alarm masks.