Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 29)

Installation
Chapter 2
2Ć17
Figure 2.10
Connection to user-Supplied Modem or RS-232-C Device
1
2
3
4
5
6
7
8
20
25
10011–I
1
User–supplied
Moderm or
RS–232–C
Device
Protective Ground
Transmitted Data
Received Data
Request to Send
Clear to Send
Data Set Ready
Signal Ground
Line Signal Detect
Data Terminal Ready
Received Data
Return
RS–232–C
CHANNEL Connector of
1775–KA Module
Set Switch 3 ON to ground pin 25. 1
Private lines are permanently connected phone lines used with modems.
Dialup is not needed. Usually the modem hold the handshake lines in the
proper states.
The RS–232 port can be connected to standard American dial–up modems
and some European modems. Other European standards specify that the
DTR signal will cause the modem to answer the phone whether it is
ringing or not, causing the phone to always be “busy”. Since the modem
port asserts DTR while waiting for a call, it cannot be used with such
modems.
The types of dial–up network modems that can be used are classified into
the following types:
Manual: these are typically acoustically coupled modems. The
connection is established by human operators at both ends, who then
insert the handset into couplers to connect the computers.
DTE–controlled answer: these unattended modems are directly
connected to the phone lines. A module controls the modem via the