If the emergency is at home and your landline number is properly registered at that address (most are), your best option is to dial from that device. 911 systems are configured to use the landline’s registered location, even older emergency systems. However, most 911 systems should now also be able to get an approximate location from your cell phone. If the problem is something that will require you to leave your home, like a fire or gas leak, use your cell phone so there is a contact number where you can be reached. If you can’t talk and can’t verbally confirm an address, calling from a landline in that location might be the most accurate for areas with older 911 systems.