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The ADTRAN ISDN Service Unit (ISU) 128 connects data terminal equipment (DTE) to the ISDN network. The ISU 128 is a full-featured single port terminal adapter that allows cost-effective high-speed data transmission at rates up to 128kbps. ISDN service is delivered from the network by a single 2-wire U-interface connected directly to the ISU 128. The ISU 128 responds to loopback commands from the telephone company central office to make testing easy.
The ISU 128 allows you to migrate existing networks to an ISDN environment. The ISU 128 interoperates with V.34 modems and Switched 56 DSUs, as well as various ISDN terminal adapters, inverse multiplexers and multilink PPP-compatible routers. (1) V.34 modem is included plus an extra modem port for an additional modem. The ISU 128 performs at synchronous data rates of 2400bps to 128kbps and asynchronous rates of 300 bps to 115.2 kbps. At rates over 64 kbps, multilink PPP or the BONDING delay equalization protocol synchronizes data over the two 64kbps B channels.