AT&T 7500 series, 7100 series, 2500 series, 7200 series manual Access and Bypass Access Tie Trunks

5-4ELECTRONIC TANDEM NETWORK (ETN) THROUGH THE ETN AND PNA PACKAGES

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Access and Bypass Access Tie Trunks

An access tie trunk is a 1-way outgoing or 2-way trunk connecting a main to a tandem switch. A bypass access tie trunk is a 1-way outgoing trunk connecting a tandem switch to a main, satellite, or tributary that is homed on another tandem switch. (Refer to figure 5-1.)Bypass access tie trunks are used when:

∙A main switch receives a high volume of calls from a distant tandem switch, and/or

∙It is more economical to route the calls over a separate bypass access tie trunk than through the tandem switch to which the main is homed.

CHICAGO

DIMENSION 2000

FINAL

NEW YORK CITY SYSTEM 85

OVERFLOW

FINAL

INTERMEDIATE HIGH

USAGE

FINAL

OVERFLOW

LOS ANGELES SYSTEM 85

PRIMARY HIGH USAGE

OVERFLOW

ATLANTA DIMENSION 2000

Figure 5-2.An Example of Intermachine Tie Trunk Usage (Overflow Routing)