The FCC requires that you register for a local number. They issued a ruling on June 15, 2009 saying that VRS providers cannot process calls from an unregistered phone after November 12, 2009. If you are unregistered, that means you do not have a local number. The reason for this is the FCC wants to be sure they are paying for calls from deaf and hard of hearing people. An IP address can be used for point to point calls, but will not be good for relay (VRS) calls after November 12th.
How do you get a local number? You need to contact the provider of your videophone to register for a local number. They will then be the default provider for that local number. This, again does not mean you are stuck with that provider for VRS calls. You can call any service provider such as ZVRS from any videophone for VRS calls. Just call 888-888-1116 and you will be connected to ZVRS!
It should be noted that local numbers are available only to deaf and hard-of-hearing people . This is part of the regulation outlined by the FCC.