Chapter 4 - Maintenance; Periodic Maintenance; Internal Reference Calibration; Common Test Procedures - Datum Systems PSM-500 Installation And Operation Manual

PSM-500/500L/500LT SCPC Satellite Modem

4.0 Periodic Maintenance

The PSM-500 requires no mandatory periodic field maintenance procedures. The unit contains
no adjustments and most calibration is digital and held in EEPROM. Should a unit be suspected
of a defect in field operations after all interface signals are verified the proper procedure is to
replace the unit with another known working modem. If this does not cure the problem, other
equipment in the link, wiring or power should be suspect.
There are no batteries or parts requiring periodic service contained within the case. The only
moving part is the internal fan, which is designed for a service life in excess of 200,000 hours.
There is no external fuse on the PSM-500 Modem. The fuse is located on the power supply
assembly inside the case, and replacement is not intended in the field.

4.0.1 Internal Reference Calibration

If desired, or if it is suspected that the modem's internal reference requires calibration, this can be
performed on a unit "on-location". A recommended interval for the reference calibration would be
after the first 6 months to a year in service and on a yearly basis thereafter. The external
reference should be of known accuracy before attempting calibration. The calibration of the
modem's internal reference from an externally applied reference is an automatic procedure
enabled from the unit's front panel. Go to <Unit: Test – Cal Ref> to enable the calibration
procedure.
⇒ Caution: The Reference Calibration procedure may result in lost traffic during
performance of the calibration! The calibration should not be performed in
operating links without prior arrangements.
Before beginning an internal reference calibration an external reference must be applied and the
<Unit: Ref – Source> must be set to "External".

4.1 Common Test Procedures

When a modem, link or system is first installed and placed in service it is common to run several
tests to verify proper performance of each of the equipment items in the link. The PSM-500 is
designed to aid in this process by providing built in test modes geared to verifying performance,
and isolating potential problems. These aids consist of the modem self test procedure, the
multiple "Loop-Back" modes available and the built-in BERT. These facilities are also useful when
troubleshooting system or link problems which involve the modem.
⇒ Caution: All of the modem operating procedures described below will result in
loss of traffic. They should not be used in operating links without prior
arrangements.
The modem self test can be used to check out a modem within a system or stand alone on a
bench. It requires nothing more than power. The procedure is described in more detail in Section
4.2.3 below.

4.1.1 Loop-Back Testing

The Loop-Back modes are typically used in a wired link with DTE equipment that can transmit
and verify receipt or preferably a Bit Error Rate Test Set (BERT). The basic procedure used is to
PSM-500/500L/500LT - Rev. 0.91

Chapter 4 - Maintenance

Maintenance
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