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IR-X.21B Connectors C-1
Appendix C
IR-X.21B Interface Module
This appendix:
• Provides a general description of the IR-X.21B interface module
• Describes the IR-X.21B connectors and pin assignments
• Describes the IR-X.21B interface module
• Describes the EXT mode for the IR-X.21B
• Describes the INT/RCV mode for the IR-X.21B.
C.1 Description
The IR-X.21B is an interface module for RAD modems, converting X.21 signals to
TTL levels. The converted data is sent over the modem link, using the modem
modulation technique, and is converted back at the other end into X.21 signals, or
into any other digital interface signal.
Figure C-1 shows a typical application of the ASM-20 standalone modem with the
IR-X.21B interface module.
Line
Central Location
DTE
X.21
Remote Location
X.21
Network
Figure C-1 Typical ASM-20 X.21 Application
C.2 IR-X.21B Connectors
Figure C-2 shows the rear panel of a standalone ASM-20 with the IR-X.21B
interface module.
DTE
X
21
Line Connector
CAUTION:
FOR CONTINUED
PROTECTION AGAINST RISK OF
FIRE, REPLACE ONLY WITH SAME
TYPE AND RATING OF FUSE.
Figure C-2 ASM-20 Rear Panel with X.21 Connector