A method and apparatus providing interconnectivity between several telephone networks. The apparatus receives a telephone transaction initiation message that originated with a telephone set located in a first network. The initiation message bears an originator's registration number identifying a subscriber whose home registration is located in a second network, the first and second networks using disparate signaling protocols. The apparatus then queries the originator's home registration database using the network protocol of the second network to determine the registration status of the originator. Finally, the registration status information is forwarded to the first network in the network protocol of the first network.