6/4/99 13:18 General Description C-1
Appendix CIR-X.21B Interface Module
C.1 General
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.2 General 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.
X.21
Network
ASM R e m o te Lo c a tio n DTE
Line X.21
RAD RAD
Figure C-1 Typical ASM-20 X.21 Application