Rockwell Automation 1785-LTx,D17856.2.1 Classic PLC-5 Programmable Controllers Users Manual - Manual (Page 68)

Choosing Communication
Chapter 5
5-10
The PLC-5 processor has two connectors that are electrically identical.
Connection to either one provides the same communication link. These
connectors are:
9-pin D-shell DH+ COMM INTFC connector
3-pin DH+ COMM INTFC connector
You can connect DH+ links to Data Highway via a communication
interface such as the 1785-KA module. The 1785-KA module allows
nodes on a DH+ link to communicate with nodes on Data Highway or on
another DH+ link.
See your local Allen-Bradley sales office or distributor for more
information on connecting DH+ to Data Highway. Also, see the Data
Highway/Data Highway Plus Protocol and Command Set, publication
1770-6.5.16, for more information.
You can connect your programming terminal to a PLC-5 processor in
several ways:
direct connect to the DH+ link
remote connection (DH+ to Data Highway to DH+)
serial connections
Direct Connect to DH+ Link
Use a 1784-KT to connect a T53 or IBM-compatible programming
terminal directly to a processor or to a DH+ link that connects processors
(Figure 5.8).
Connecting a DH+ Link
to Data Highway
Choosing Programming
Terminal Connection