Abstract: The invention is an adaptor which permits using a digital telephone device with an incompatible telephone network access. In its most preferred embodiment, the present invention is an adaptor which permits an ISDN telephone device to exchange digital data with two Switched-56 Access. An ISDN Basic Rate Access interface circuit interfaces with the ISDN telephone device, while two Switched-56 Access interface circuit interfaces with two Switched-56 Access. The adaptor also includes a clock recovery circuit for synchronizing digital data transfers occurring between the ISDN Basic Rate Access interface circuit and the ISDN telephone device with the digital data transfers occurring between the Switched-56 Access interface circuit and the Switched-56 Access.