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UPLC™ Application Manual
For example, let's say your remote is set for auto-
matic periodic testing, with a period of eight
hours. If it does not receive a checkback test with-
in eight hours and five minutes, it executes a
checkback test. If this test is successful, both the
master and the remote's periodic timers are restart-
ed at roughly the same time, and the master takes
over for subsequent checkback tests, if both units
are set for the same periodic interval. The period-
ic timer starts as soon as the unit is powered, so
that one will have a head start on the others. After
the first successful checkback test, all the periodic
timers in the network are synchronized, and the
master initiates any future tests.
If you have more than one remote in your system,
each has its own unique grace period. Remote #1
waits five (5) minutes, remote #2 waits 10 min-
utes, remote #3 waits 15 minutes, and so on.
For example, if neither remote #1 nor the master
has initiated a checkback test for the interval plus
10 minutes, remote #2 executes a test.
For this scheme to work properly, it is important to
keep all the settings similar. If the master is set for
automatic periodic testing, all remotes should also
be set this way. If not, you may have more check-
back tests occurring than you would expect at
equally unexpected times. Also, the four execution
times should be the same for all units in the sys-
tem.
7.5.6 Remote-Initiated Timed Tests
Just as with remote-initiated periodic testing,
remotes set to timed testing initiate their own
checkback tests if the master does not do a test in
time. The "grace" period is longer for this mode:
Primary Mode
Coded
Coded
Timed
Timed
Page 7–8
Table 7–1. Primary/Fallback Communications Options.
Fallback Timed
Disabled
Enabled
Disabled
Enabled
user time + 10 minutes for remote #1, user time +
15 minutes for remote #2, etc. That allows this
scheme to work even when there is up to five min-
utes difference between the checkback units'
clocks.
For automatic timed testing, the clocks in the mas-
ter and the remotes should be fairly close.
You can enable the automatic clock synchroniza-
tion feature to keep your clocks synchronized.
When enabled, the master synchronizes all remote
clocks to its own time starting at 12:30 a.m. In
practice, the synchronization is rough, within
about +/- 2 seconds, but that is sufficiently accu-
rate for timed checkback testing.
7.6 Checkback Test Options
A single checkback test is a set of encoded data
messages, a simple keyed carrier signal, or a mix-
ture of both. You have several options for perform-
ing this test:
• Keyed carrier timed test
• Encoded carrier test
• Primary and fallback communication
modes
• Communication retries
7.6.1 Keyed Carrier Timed Tests
This is the classic method where the checkback
simply turns on the carrier for a specific interval of
time. Each unit in the system is assigned a unique
time and can recognize when the carrier has been
on for the correct interval. The correct unit
Description
No more tries after max retry count
Makes one last try using Timed Mode
No more tries after max retry count
No more tries after max retry count
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Troubleshooting
