ADTRAN ISU 128 - Manual (Page 19)

Chapter 1. Understanding ISDN and the ISU 128
4 ISU 128 User Manual 61202.029L2-1
ISU 128 INTEROPERABILITY
Telephone networks are evolving from analog technologies to digital technol-
ogies such as ISDN. This transition is time-consuming and costly for the tele-
phone companies. Upgrading all locations and facilities is a lengthy process.
The ISU 128 bridges this transition by supporting communications with exist-
ing and future network services and equipment. The ISU 128 supports com-
munications with Switched 56 service, Switched 56 DSUs (2-wire and 4-wire),
various ISDN terminal adapters, ISDN terminal equipment, BONDING com-
patible inverse multiplexers, and analog modems with the optional V.34 mo-
dem (part number 1202029L3).
Figure 1-3 illustrates the ISU 128 operation in various switched network ser-
vices and customer premises products.