Using with Campbell Scientific Dataloggers
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with Nokia GSM phones, the modem setting may need to have the extra codes
"X0" added to the initialisation string to ensure correct operation.
The baud rate for connection should be set to 9600. Any existing initialisation
strings specified in MODEM.INI or in PC208W’s modem set-up will still apply,
but it may be necessary to add additional settings to limit the connection protocols.
This is because, in practice, some of the newer high-speed modems have been
found to attempt to negotiate connections that cause the GSM network modem to
immediately drop the line. For connection on a GSM network the modem only
needs to establish a 9600 baud, V32 connection. For many recent Hayes
compatible modems this is set by adding ‘S110=0’ or the cMS=9 at the
end of any existing initialisation string. In addition, some networks will reject calls
if data compression is enabled. These functions are controlled by the initialisation
strings sent to the modem.
For LoggerNet Version 2.0, providing the modem is installed under Windows
correctly, it should be simplest to use the TAPI interface option and select the
modem from the TAPI line option that shows the installed modems.
While Campbell Scientific Ltd may be able to give some advice as
to the best settings to use for common modems, the connection of
the landline modem to a cellular network is specific to the cellular
network being used. Problems establishing the connection are often
not related to the fact that a TC35T or datalogger are connected at
the remote end of the connection, but are caused by compatibility
issues of the PC modem with the network. Please also contact your
cellular network support team for advice on any problems that you
might encounter.
6.3.2 Configuring the TC35T as a Base Station using PC208W
The TC35T should first be set up as if it were to be used with a datalogger (see
section 6.1 above). Although some older versions of software may work, we
recommend that PC208W Version 3, Loggernet 2.0 or later versions are used. The
instructions below apply only to such software.
To use the TC35T, after the initial set-up, connect the modem to the PC then run
PC208W. Choose the ‘Setup’ screen and add a phone modem to a COM port. Select
the modem type ‘Default Modem’ and select ‘Edit Modem Strings’. Overtype the
name of the modem to make it read ‘TC35T’. The only other setting you need to add
is a "+CBST=n,0,1" command to the end of the ‘Modem Initialisation’ string, where
n is network specific, e.g. the previously set value of 7 will work but some networks
recommend 71 to force a digital connection which can reduce the connection time.
See the PC208W manual for further advice — Appendix A will give specific
advice on using and adding modems, initialisation strings, etc.
6.3.3 Extending the Default Time-Outs
When using either a landline base modem or a TC35T as the base, it is sometimes
necessary to add “S7=45” to the end of the modem initialisation string. This setting
extends the time both the PC and the base modem will wait before timing out an
attempted connection to a remote modem to 45 seconds. This setting may also be
required for normal desktop base modems. The default setting for the PC software
is 30 seconds, which can be a little short if the GSM network is busy. Normally you
are allowed to increase this setting up to 60 (seconds) if a call is seen to take such a
long time to connect. Setting too long a delay may, however, slow down the retry
sequence in the event of a failed connection.
NOTE
