PSM-500/500L/500LT SCPC Satellite Modem
Installation
PSM-500/500L/500LT - Rev. 0.91
Page 2-11
2.3.6.1 Set-Up Procedure for 1:1 Redundancy
If redundancy mode is to be set up between a pair of modems then the following procedure is
followed during installation, other wise this section can be skipped. In overview the procedure is:
1. Physically install both units to be paired and connect the IF transmit and receive
coaxial cables and data cables to both units. The special data “Y” cable is connected
between the redundant pair. For convenience we will arbitrarily call one modem
“Primary” and the other “Secondary”.
2. Power-up and configure the primary modem completely for the intended operating
parameters, including setting the
<Unit: Redundancy – Mode>
parameter to “1:1”.
This initial unit should not be in alarm. The second unit should still be turned off.
3. Turn the power on the secondary unit on.
4. Go to the primary unit menu item
<Unit: Redundancy – Config>
and press the
“Edit” key. The on-line unit will ask permission to transfer configuration to the second
unit with the prompt “Config Backup?” Confirm by pressing “Enter”. The primary unit
should say “Sending Config” for approximately 1 second. If the transfer of any packet
results in an error, a “Send Fail” message will be displayed, but transfer will continue.
5. Verify that the units are functioning correctly in redundancy mode. Go to the
<Unit:
Status – Redundancy>
item in both units. The on-line unit will say “On-Line, Bckup
OK” while the off-line unit will say “Standby, OK”.
Physical installation of the two units is best accomplished with one unit directly above the other in
the rack. This allows the status of the two modems to be seen together and avoids confusion.
Care should be taken that both units are not turned on in a non-redundant configuration with the
“Y” data cable installed. This will result in the two unit’s data output drivers possibly conflicting
and causing damage.
During configuration of the primary unit several new parameters will become available after the
mode is set to 1:1. In addition to the
<Unit: Redundcy - Config>
parameter of step 4 above
there will also be parameters that allow the alarms and timing to be configured for the application.
The default values for these parameters are probably good in most installations, but they may
require specific configuration, especially if the unit had been configured for another unique
application. These new parameters are:
•
<Unit: Redundncy – Sw Rqst>
This parameter allows you to determine which alarm
indications result in a switch request. The possible selections are “On Any Alarm”, “On
Alarm A”, “On Alarm B”, or “On Alarm A & B”. Since the specific alarms which comprise
Alarm A and Alarm B are programmable themselves, then a switch request is highly
programmable itself. For most applications though the default “On Any Alarm” is a
preferred selection.
•
<Unit: Redundncy – Sw Hold>
This parameter determines how long an alarm must
exist on the on-line unit and not the off-line unit before switching will occur. Allowable
values are 0.0 to 600.0 seconds. The value could be set to zero, but this is not advised. A
nominal value of 0.5 seconds insures that intermittent cases do not cause undue
switching. A built in factor of 10 seconds is provided once a switch has occurred before a
switch back to the original unit is allowed (except in the case of a manual switch request
or loss of power in the on-line unit which requires 2 seconds).
Teardown or un-pairing of two redundant units is accomplished by turning both units off before
removing the “Y” cable. Then power on and set the
<Unit: Redundancy – Mode>
to “Disabled”.
A unique case can arise when both units are off-line and powered up at the same time. They will
probably go out of alarm at virtually the same time. In such tie cases, which unit will be placed on
line is determined by the unit serial numbers, where the highest serial number wins the tie.
