ADTRAN DSU IV ESP User Manual page 20

Chapter 1. Introduction
2
The DSU IV ESP provides both V.35 and EIA-232 electrical and
physical DTE interfaces to accommodate a variety of applica-
tions.
To ensure a reliable connection, the unit features an extended
receiver capability which permits operation over long loops
(3.4 miles or 5.5 km of 26 AWG at 56 kbps).
The ESP 4-wire SW56 DBU card and the base unit's integrated
SW56 capabilities are compatible with AT&T Accunet and Sprint
SW56 type services. The V.34 DBU card allows switched backup
over the public switched telephone network (PSTN). The ESP
ISDN 1B+D card is compatible with National ISDN and supports
a U- interface to the Basic Rate ISDN.
Figure 1-1 shows a typical point-to-point application for the DSU
IV ESP.
DSU IV ESP User Manual 61204.011L1-1