Specifications
46 Rockwell Automation Publication AG-SG001G-EN-P - April 2015
Chapter 3 Choosing Data Communication Equipment
Telephone Modem and ISU Installation Guidelines
Telephone modems and ISUs require a telephone-company approved connector.
Consult your modem/ISU vendor for installation requirements.
Choosing a Radio
Transmission System
You can use radio modems for point-to-point, point-to-multipoint, or
multipoint-to-multipoint applications.
The primary consideration for radio modems is the radio frequency band in
which they operate. You can choose among the radio types in this table.
Also, consider the following criteria when selecting radios:
• Serial or Ethernet communication
• Range/distance of area to be covered
• Required communication rate
• Licensed fixed frequency or unlicensed spread-spectrum radio
• Space requirements
– Do you need a chassis-mounted or standalone modem?
• If serial communication, requirements of the DTE devices to which you
are connecting
– Do you need asynchronous or synchronous operation?
– What interfaces do you need (RS-232, MIL 188, EIA-449, IEEE 488,
CCITT V.24)?
– What other features are required to support your DTEs?
• Required remote diagnostic features
Radio modems can either be crystal-based or microprocessor based.
Microprocessor-based modems can be more easily serviced and
programmed from a central control site. Diagnostics can be performed at
the control site, allowing technicians to diagnose problems without having
to travel to the remote site.
• Power availability at the remote sites
• Required licensing
Radio Type Frequency
VHF 66…79 MHz
150…174 MHz
UHF 450…470 MHz
Higher frequency UHF 850…960 MHz
Microwave 1 GHz and above
TIP
If you are using all Allen-Bradley DTE devices, choose an
asynchronous modem interface.
Radio
Modem
Radio
Modem