These network modules utilize either the single or dual ISDN Primary Rate Interface (PRI) network module to offer support for up to 60 remote modem users (using two network modules), at speeds up to 56 kbps. Each network module supports up to 30 digital modems. Flexible LAN topologies, including Ethernet, Fast Ethernet, and Token Ring, are supported. The benefit is the support of 60 digital modems in a space-saving (2RU) chassis.The internal digital modem network module is available with 6, 12, 18, 24, and 30 modems preinstalled, and it can be upgraded on site, from say 18 to 24 modems, as simply as upgrading computer memory! This feature gives the maximum flexibility to grow a dial-in solution as the remote user base grows.