In order for a GSM gateway to work correctly, we need to establish two important facts.

How will the gateway connect to my PBX ?

This could be an ISDN 30 connection, ISDN2, SIP or Analogue.

Do I have a strong signal from my chosen Network in the room where I want my gateway to be sited?

This information is generally collected by an engineer performing a site survey; however by selecting the Service tabs on the RHS you will gain some understanding about the information he will be collecting.