RIO Remote I/O System User Guide
Installing a Long Distance Module (LDM)
Page 188
Chapter 2 Installing hardware and software
Synchronous X.21 connection
Note
Any connector pins not listed in the next table must not be connected.
DB25 female (LDU) DB15 male (Modem)
Pin Signal Description Pin Signal Description
1Chassis Chassis ground 1Chassis Chassis ground
7GND Ground 8GND Ground
9DCD+ Data Carrier Detect 5Indicate+ Indicate+
10 RXD- Inverse RXD 11 RXD- Inverse RXD
11 RXD+ Receive Data 4RXD+ Receive Data
12 TXD- Inverse TXD 9TXD- Inverse TXD
13 TXD+ Transmit Data 2TXD+ Transmit Da ta
21 DCD- Data Carrier Detect 12 Indicate- Indica te-
22 DTR+ Data Terminal Ready 3Control+ Control
23 DTR- Inverse DTR 10 Control- Inverse Control
24 RXC- Inverse RXC 13 Clock- Inverse clock
25 RXC+ Receive Clock 6Clock+ Clock
Telephone line
DB25 female to DB15
male adaptor.
DB25 female flying lead
to remote site LDU
DB25 female flying lead
from host card site LDU
DB25 female to DB15
male adaptor.
X.21
Asynchronous
modem at host
card site
X.21
Asynchronous
modem at
remote site