Campbell Scientific COM220 56k Phone Modem - Manual (Page 18)

COM220 Telephone Modem
Some of the AT command settings that may be changed 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 partly 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 cannot/do not 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.
CCITT 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 (that is, 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 (such as the CR510, CR10X, CR23X,
CR7, and CR5000), verify that DIP switch 1 on the COM220 is in the
open (modem enable) position. For PakBus dataloggers (such as the
CR800, CR850, CR1000, CR3000, CR10XPB, 23XPB, etc.), DIP switch 1
can be in either position, but closed (SDC7) is preferred. See Appendix
A.1, DIP Switch Settings, for details.
3) If the COM220 is set for modem enable (DIP switch 1 open), verify that
the ME baud rate selected (DIP switches 3 and 4) agrees with related
communication instructions in the datalogger program. Instructions for
setting the COM220’s ME baud rate are found in Appendix A.1, DIP
Switch Settings.
4) If the COM220 is set for modem enable (DIP switch 1 open) and you are
unable to connect to the datalogger, try setting the datalogger ME baud
rate, BaudrateME, to a negative number (for example, –9600) in order to
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