Patent ID: 7142549

Claim:
An interface device for providing a gateway function between lines of a public switched telephone network (PSTN) that carry digital hierarchy signals in a plurality of digital hierarchies and an asynchronous transfer mode (ATM) backbone network that carries signals in ATM format, the interface device comprising: a telephony transceiver operative to receive upstream digital hierarchy signals in a plurality of digital hierarchies from the PSTN; a hierarchy converter operatively associated with the telephony transceiver to receive said upstream digital hierarchy signals in a plurality of digital hierarchy signals and operative to convert at least some of said received upstream digital hierarchy signals to upstream signals in a single digital hierarchy distributed over a plurality of logical channels; an inverse multiplexing unit operatively associated with the hierarchy converter to receive said upstream signals in the single digital hierarchy distributed over a plurality of logical channels therefrom and operative to inverse-multi-plex said received up-stream signals thereby to form upstream inverse-multiplexed digital hierarchy signals; an ATM framer operatively associated with the inverse multiplexing unit to receive said upstream inverse-multiplexed signals therefrom and operative to map at least some of the upstream inverse-multiplexed digital hierarchy signals into ATM cells thereby to form upstream signals in ATM format; and an ATM transceiver operatively associated with the ATM framer to receive said upstream signals therefrom and operative to transmit said upstream signals in ATM format to the ATM backbone network.