RAD Data comm ASMi-31 operation manual Appendix C Interface Module, X.21 Connectors

Appendix C

X.21 Interface Module

C.1 General

IR-X.21 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.

ASMi-31 is generally supplied with IR-X.21. This is due to an internal FIFO that assumes the phase mismatch when the clock is supplied by an external source. ASMi-31 also has the option to order IR-X.21 for extra buffers.

Figure C-1shows a typical application of the ASMi-31 standalone modem with the IR-X.21 interface module.

Figure C-1 Typical ASMi-31 X.21 Application

C.2 X.21 Connectors

Figure C-2shows the rear panel of a standalone ASMi-31 with the IR-X.21 interface module.

Line Connector

Figure C-2 ASMi-31 Rear Panel with X.21 Connector

The ASMi-31 modem rack version requires an additional adaptor to connect between the DB-15 connector of the X.21 equipment to the DB-25 connector of the ASM-MN-214 modem rack. For this purpose, an optional DB-15 attachment CIA/X.21 can be ordered separately from RAD. The attachment connects to the ASM-MN-214 rear panel as shown for the CIA/V.35 attachment in Chapter 5.

X.21 Connectors C-1

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