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CDM-550T Satellite Modem
1.1.4
Data Interfaces
The CDM-550T includes, as standard, a universal data interface which eliminates the
need to exchange interface cards for different applications. The interfaces offered include
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1.2
Options
As an external option, a G.703 interface (Comtech EFData Model Number CIC-50),
operating at T1 (1544 kbps) and E1 (2048 kbps) is available.
Two optional Forward Error Correction Codecs can be supplied. The first, a Reed-
Solomon Codec (a plug-in daughter card, field upgradeable), significantly enhances the
bit error performance of the modem. The second is the Comtech EFData Turbo Product
Codec, representing a very significant development in the area of FEC. Like the RS
Codec, it is a plug-in daughter card, field upgradeable. It provides the best level of BER
improvement currently available, and in Rate 3/4 QPSK mode, simultaneously conserves
bandwidth.
1.3
Compatibility
For 1:1 applications the CDM-550T is supported by a low-cost external switch, the CRS-
100. For Hub applications, the CDM-550T is supported by a low-cost 1:N switch, the
CRS-200. Its fast acquisition time makes it attractive for both demand-assigned and
fixed-assigned SCPC applications.
The CDM-550T is a companion product for the Comtech EFData line of RF
Transceivers. The Modem incorporates an FSK serial link that can be activated on the
Receive IF port for the purpose of communicating with a Transceiver, if connected. In
this manner, a user may monitor, configure, and control the Transceiver, using the front
panel display and keypad of the Modem. The EDMAC channel may also be used to
convey M&C data to a Transceiver at the distant end of a satellite link, if it is connected
to a CDM-550T.
The CDM-550T is fully backwards-compatible with the Comtech EFData CDM-500 and
CDM-550 modems.
Rev. 1.3
EIA-422 (EIA530) DCE
V.35 DCE
Synchronous EIA-232 DCE
Asynchronous EIA-232 (at data rates up to 56 kbaud)
X.21 DTE and DCE
Introduction
1–3
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