If your business needs have you out in the middle of nowhere, there might not be an Internet connection. As long as your cell phone has signal, that's all you need to connect a VoIP Phone system!
GSM Gateways use a SIM card and connect with a cellular tower. They convert the cellular connection to SIP and provide the connection as a trunk to a VoIP PBX. The number of SIM cards a gateway can hold determines how many calls you can make.
GSM Gateways are perfect for redundancy, T1 outages, or as a connection in places where inexpensive analog or SIP connections are not available. They are ideal for remote locations where you have cellular connection but no Internet. If need be, with a GSM Gateway you can create and run you entire remote phone system off of back up power and a cell tower. For added assurance, you can add on a Go3 No Questions Asked replacement warranty!