Hi
My Application working successfully with these settings I am using GSM Modem.
Try it once
<appSettings>
<add key="connstring" value="Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\SENDSMS\Mobiles.mdb" />
<add key="COMPORT" value="1" />
<add key="BAUDRATE" value="9600" />
<add key="TIMEOUT" value="300" />
<add key="ISFORTESTING" value="false" />
</appSettings>