Modem Configuration is allocated for GSM modem configuration. If you need SMS alert for different events like DAS ON/OFF, Device status etc., then you need to configure GSM modem in the Modem configuration.

To open Modem Configuration Follow below Path:

Go to Master Configuration→Other Configuration→Modem Configuration.

Click on Add new button to Config new modem. 

You will get configuration page as shown below.

You have to configure all serial parameters according to the GSM modem and click on save button.