From the original program listing, reproduced here for reference:
GXW4501 Beta Test
The GXW4500 series are E1/T1/J1 Digital VoIP Gateways that allow digital PSTN and ISDN trunks to be integrated with VoIP networks. By connecting the GXW4500 series with a VoIP network and a traditional PBX or E1/T1/J1 provider, businesses can drastically increase the amount of PSTN/ISDN trunks integrated with their VoIP network and the concurrent calls supported. The GXW4500 series offers three models that provide 1, 2 or 4 T1/E1/J1 spans and support 30, 60 or 120 concurrent calls to cater to the VoIP needs of large and medium sized enterprises.