Data Interfaces
SDM-2020 Satellite Demodulator
A–24
Rev.3
Notes:
1.
In loopback TX, data is routed through as much of the interface card as
practicable before being returned to the RX interface.
In a modulator chassis, TX
data continues to enter the modulator and is transmitted during loopback. In the
demodulator, satellite data is interrupted during loopback and the data entering
the TX connector is returned to the RX connector. Demodulator data from the
satellite is not routed to the modulator by the data interface.
2.
Loop-Through Mode (Modulator Only); is the same as loopback only the yellow
TEST MODE LED is not activated.
3. Rev. A or later assemblies include this capability. Rev dash (-) assemblies can be
upgraded to this capability.
A.4.3 User
Interfaces
The following paragraphs describe the electrical and physical properties of the ASI/RS-
422 data interface module.
A.4.3.1
Transmit Input Connectors, J3/J4, BNC, Female
These two connectors accept TX data from the terrestrial interface. By default, J3 is
enabled and J4 is disabled. The active input is user programmable and maintained in non-
volatile memory of the modulator or demodulator chassis. Both connectors are terminated
into 75
Ω
, whether selected or not.
A.4.3.2 RS-422
Connector, J5, 25-Pin D, Female
This connector is compatible with EIA-530 operation and pin-out. It is a serial interface
with RS-422 signals plus the TTL-OC fault signals indicating the status of the modulator
or demodulator.
A.4.3.2.1
Connector Pinout, J5
The connector is a 25-pin, female, D type, with threaded jack nuts (refer to Table A-12
for connector pinout).
Notes:
1.
RS-422 signal levels are as defined in RS-422.
2.
The differential sense of all signal pairs is a logic “1” when “A” is negative with
respect to “B.”
Summary of Contents for SDM-2020
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Page 35: ...SDM 2020 Satellite Demodulator Installation Rev 3 2 3 Figure 2 1 Typical Rack Installation...
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Page 212: ...SDM 2020 Satellite Demodulator Glossary Rev 2 g 3 W Watt...
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