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COM220 Telephone Modem
1. Introduction
1.1 General Description
The COM220 modem is a selectable-baud-rate modem employing the Hayes
AT command set. Its primary use is as a remote site phone modem connected
to a CSI datalogger. The modem is powered and enabled by the battery-
powered datalogger. When not active, the COM220 draws 100 to 120 µA
from the datalogger’s 12 VDC output. During a call, it draws about 30 mA.
The COM220 is a replacement for the COM210. However, the COM220
supports both synchronous device communication (SDC) and modem enable
(ME) communication, as well as various ME baud rates (9600 to 115200).
The default settings for the COM220 at shipping are SDC7, and PakBus ready
(see Appendix A for details).
The default settings ARE NOT compatible with dataloggers
that have non-PakBus operating systems (e.g., CR510,
CR10X, CR23X, CR7, CR5000). However, compatibility
with non-PakBus dataloggers is easily achieved by
changing DIP switch settings (Figure 1). If you want to use
the COM220 as a drop-in replacement for the COM210,
the COM220 settings should be changed to modem enable
(DIP switch 1 open), and 9600 baud (DIP switches 3 and 4
open). In addition, DIP switch 5 must be closed for
connection to non-PakBus dataloggers. Instructions for
configuring the COM220 are described in Appendix A.
IMPORTANT
FIGURE 1. COM220 DIP Switches. Five Screws and the Outer Cover
Must be Removed for Access to the DIP Switches.
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