The ISDN BRI DIM also provides dial backup access to the public switched telephone network (PSTN) via ISDN BRI interfaces at rates of 64kbps. For easy upgrades, all these modules are field upgradable and can be configured remotely eliminating the need for remote technical expertise. ADTRAN, the leader in WAN connectivity offers proven and dependable equipment that will increase your network performance, lower costs and migrate to next generation technologies.