Campbell COM220 Instruction Manual - 5.  Troubleshooting

COM220 Telephone Modem 

You can modify the following COM220 settings with DIP switches: 

1) Communication mode (e.g., SDC or Modem Enable) 

2) ME baud rate 

3) PakBus ready 

Additional changes (see examples below) may be modified with Hayes AT 

commands.  Appendix A.2 describes the procedures and commands required to 

effect the changes described in this section.  

Some of the AT command settings one may change are: 

Disable auto-answer:  This option is used only when the modem is not to 

answer a call.  For example, the COM220 is connected to a telephone line that 

is to be used part time for voice communication.  In this situation it is best to 

have the datalogger call the computer. 

Speaker On/Off and Volume:  Default settings have the speaker on only 

during call establishment and set to a low volume.  The speaker may be turned 

completely off in order to limit the current drain during the connection or so 

you don’t hear the speaker.  It is also possible to set the speaker volume higher, 

if you want to hear the speaker better than the default low volume setting. 

Answer on X

th

 ring:  This option is used when the modem is sharing a line 

and you only want it to answer after a specified number of rings.  For example, 

the COM220 is sharing a line with people at an office.  It can be programmed 

to only answer after the third ring.  If the PC calls when the office is closed and 

no one answers the phone after three rings, the datalogger will pick it up. 

Change telephone system types:  Change from the Bell 212A (U.S. and 

Canada) system to a CCITT V.32 (foreign, 9600 baud) or CCITT V.22 

(foreign, 1200 baud) system.  This does not mean that the COM220 is tested 

and approved for all foreign countries. 

CITT is an international consultative committee that sets international 

communications usage standards.  V.32 and V.22 are CCITT standards that the 

COM220 meets. 

5.  Troubleshooting 

When the Campbell Scientific software cannot establish a link to a remote 

datalogger that is connected to a COM220, check the following: 

1)  Verify that the modem initialization settings on your computer are correct 

for your specific calling modem (i.e., the modem attached to your 

computer).  See the calling modem’s software manual and/or help screens 

for more information. 

2)  If using a non-PakBus datalogger (e.g., CR510, CR10X, CR23X, CR7, 

CR5000 with array-based operating system), verify that DIP switch 5 on 

the COM220 is in the CLOSED position.  For PakBus dataloggers (e.g., 

CR800, CR850, CR1000, CR3000, CR10XPB, CR23XPB, CR510PB), 

DIP switch 5 should be open.  See Appendix A.1 for details. 

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