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1.3
Features
1.3.1
Physical Description
The CDM-425 Advanced Satellite Modem is constructed as a 1RU-high rack-mounting chassis,
which can be free-standing if desired. Handles at the front ease placement into and removal from
a rack.
The CDM-425 Advanced Satellite Modem chassis assembly (CEFD P/N PL-0021674 Standard
AC Chassis or CEFD P/N PL-0021408 Optional DC Chassis) is physically comprised of two main
card assemblies:
•
Baseband Framing Card. This first card includes all of the interface circuits, the
framer/de-framer, plesiochronous/Doppler buffer, high-level data link control (HDLC)
framer, Ethernet switch, and the main microcontroller.
•
Modem Card. This second card is the modem itself. It performs all signal processing
functions of modulation, demodulation, and primary FEC.
1.3.2
Modem Compatibility
The CDM-425 Advanced Satellite Modem is fully backwards compatible with the Comtech EF
Data CDM-625 and CDM-625A modems in VersaFEC modes. It is also backwards compatible
with the CDM-625A in VersaFEC-2 modes.
1.3.3
Verification
The CDM-425 Advanced Satellite Modem includes many test modes and loopbacks for rapid
verification of the correct functioning of the unit. Of particular note is the IF loopback, which
permits you to perform a quick diagnostic test without having to disturb external cabling. During
the loopback, all of the receive configuration parameters are temporarily changed to match those
of the transmit side, and an internal RF switch connects the modulator output to the demodulator
input. When normal operation is again selected, all of the previous values are restored.
1.3.4
Updating Modem Firmware
Chapter 4. UPDATING FIRMWARE
The CDM-425 Advanced Satellite Modem stores its firmware internally in flash memory, which
simplifies the firmware updating process without having to open the modem. Firmware downloads
are available via the Internet from Comtech EF Data's Web site, via e-mail, or on CD, and can be
transferred from an external client PC once connectivity has been established with the modem.
Introduction
CDM-425 Advanced Satellite Modem
1–4
Revision 0
MN-CDM-425
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