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SYSTEM DESCRIPTION, INSTALLATION, AND MAINTENANCE MANUAL
MCS--4200/7200 Multi--Channel SATCOM System
2
The SDU defers testing of sensitive equipment until a positive indication of
settling is detected, or sufficient time passes so the lack of settling itself can
be classified as a failure. Deferral of these sections of POST also result in
normal operation being deferred, including access to the user interfaces
(SCDU, CFDS, and CMT) and all automatic calibration processing.
Consequently, the SDU suspends POST until the SDU detects the first of
the following conditions:
• OCXO heater monitor indicates it has achieved operating temperature.
• Power supply unit (PSU) temperature sensor indicates a reading above
25 °C.
• Channel filter module transmit and receive PLO lock detectors both
indicate that lock has been achieved.
• More than 4 minutes have elapsed since primary power was applied.
(c) LRU Front Panel LED and Alphanumeric Display Tests
1
A test of the HPA and HSU front panel LEDs is performed as a part of each
POST. At a minimum, this is made up of flashing the LEDs on and off. The
LED flashing continues until POST is completed or for 3 ± 0.5 seconds.
During the test, the SDU tests its alphanumeric display by incorporating one
or more occurrences of the word TESTING into its display sequence to
make sure all display elements are tested.
(d) RF Loop Back Tests
1
As part of the system-wide POST, the SDU implements a RF loop back test.
The RF loop back occurs in the radio frequency module (RFM) installed in
the SDU.
2
The SDU delays initiating the RF loop back test until it receives an indication
the RF loop back has been activated. If the SDU fails to receive a valid
indication within 30 seconds following the RF loop back request, then the
SDU completes its POST without executing the RF loop back test. The SDU
cancels the RF loop back request when the loop back test is completed, or if
the 30 second timer expires while waiting for verification of an active RF loop
back.
(3) Person-Activated Self-Test
(a) The person-activated self-test (PAST) performs the same functions as POST.
PAST is initiated in the HPA and the HSU by pushing the PUSH-TO-TEST (PTT)
switch on the respective LRU front panel. PAST can also be initiated any time
through:
• Respective CMT interface to the LRU
• SSM field of the HPA command word sent to the HPA from the SDU
• BIT request in HSU command word sent to the HSU from the SDU.
Honeywell International Inc. Do not copy without express permission of Honeywell.
23- -20- -35
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15 Jul 2006
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