Specifications

Introduction D-1
Appendix D
IR-X.21Interface Module
D.1 Introduction
IR-X.21 is an interface module that converts 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 D-1 shows a typical application of FOM-40 with IR-X.21 interface module.
FOM-40 FOM-40
Fiber Optic Cable
Router Router
X.21 X.21
Figure D-1. Typical Application of FOM-40 with IR-X.21 Module
Standalone FOM-40 Connector
Figure D-2 shows the IR-X.21 interface module. Table D-1 lists the module DB-15
connector pin assignment.
Figure D-2. IR-X.21 Module
Table D-1. IR-X.21 Connector Pin Assignment
Pin ID Function
1 Shield Chassis connection
2 A Transmit signal A
3 A Control A
4 A Receive A
5 A Indication A
6 A Signal timing A
7 A External Timing
8 GND Common