If you modem goes offline frequently, it may be due to a temporary lost carrier. To lengthen the time the modem will go offline after the carrier is lost, change the modem properties.
01. Open up the Control Panel
02. Double click on the Modem icon
03. Click on Properties / Connection / Advanced
04. In the Extra Settings, enter S10=10
05. This will enable the modem to stay connected without a carrier for up to 10 seconds.