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PSM-500/500L/500LT SCPC Satellite Modem
Maintenance
4.5 Frequently Asked Questions - FAQ
OR How Do I?,
Why Doesn't It?,
and Where Is?
This Section is intended to form a smart index pointing to proper sections of the manual with
information on performing common actions or answering common questions. The presentation
here is divided into 5 common areas – Link Setup, Front Panel, Remote Control, Data Interface
and Manual.
A. Link Set Up and Installation.
A.1 Compatibility with other Modems.
How do I make the PSM-500 talk to a xxxx brand modem on the other end of a link?
The PSM-500 has several new programmable features which should make this easier than ever.
First, where possible if both modems adhere to Intelsat IESS standards then those defined
parameters should be set the same. Still all modem manufacturers have their own conventions
for setting parameters with no specified standard, so for example some modems may have a
different modulation sense for data bits than others. This would make no difference between two
modems of the same type, but would invert data between modems of different types on each end
of a link. Most items of this type are programmable in the PSM-500 modem.
The PSM-500 also has a significant number of FEC compatibility modes for aid in achieving
compatibility with some competitive modems, especially in Turbo FEC modes. These modes are
denoted by the FEC Option type "CT" on the front panel selection.
Is Datum Systems' Turbo Product Codes compatible with that made by other modem
manufacturers?
The PSM-500 also has a significant number of FEC compatibility modes for aid in achieving
compatibility with some competitive modems, especially in Turbo FEC modes. These modes are
denoted by the FEC Option "CT" on the front panel selection. These modes are typified by the
modes used in the CDM5xx and CDM6xx series of competitive modems.
There are several modes that are probably not compatible for several reasons. First is
that there is no standard for implementation of TPC. Second, Datum Systems spent a lot
of time and development in implementing a full set of TPC parameters (i.e. Rates 1/2, 3/4
and 7/8), and insuring the absolute best performance with no compromises. We have
seen no other TPC implementation that even comes close to ours. Third, because we
have many customers that use our modems in systems requiring low latency we
implemented an alternate "Short Block" mode that reduces the typical TPC delay by
approximately 1/3. The techniques used in this TPC achieve the best performance of any
modem currently produced. Our latest TPC "Advanced" modes are also proprietary to
Datum Systems, simply because we know of no one else using the specific parameters.
Is the PSM-500 Remote Control Protocol Compatible with the PSM-4900?
The PSM-500 has significant new capabilities and features that cannot fit into the structure of the
PSM-4900 protocol. However, the PSM-500 will respond to properly formatted PSM-4900 binary
control packets within the capabilities of the PSM-4900. This allows mixed systems of 4900 and
500 series modems without initially changing control software. The compatibility does not
currently extend to operation over the link on the MCC channel.
Page 4-15
PSM-500/500L/500LT - Rev. 0.91
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