Rockwell Automation 2708-DH5B2L_DH5B4L Attended Workstation - Manual (Page 74)

Chapter 7
Network Design
7–4
It is possible to configure a network which spans multiple buildings, outposts
or sub-stations located at remote sites. Switched (dial-up) or leased telephone
lines (also referred to as ‘Common Carrier’) can be used with asynchronous
modems to provide communications for such a network.
Asynchronous short-haul modems may be used to extend the normal RS-232
communication distance from 100 feet to as much as several miles. The only
modem recommended for networks over dial-up telephone lines is a 212-A
compatible modem.
①
To use modems for communications between a Concentrator and Submaster,
the workstations must have the RS-232 communications port and a modem
cable connected for TXD, RXD, RTS, CTS, DSR, DTR and GROUND (see
Chapter 2). The COMM BAUD RATE parameter must be changed from
9600 baud to whatever baud rate is correct for your modem. As soon as the
modems establish communications between themselves the remote system
will be ready for use.
A Concentrator which has not yet been connected via modem to the
Submaster will display:
mm–nn READY/ONLINE [C] ?
When the Submaster does respond, the ? is removed to display:
mm–nn READY/ONLINE [C]
① A “Hayes-compatible” modem is a good choice.
Extending Networks
Over Phone Lines