Administrator's Guide

Features and technical reference
555-233-5061908 Issue 5 October 2002
Applications for different trunk types
To help you select the right type of trunk for a specific application, the following
table gives you an overview of key characteristics of different trunk groups.
Remember that all analog trunks can carry only voice and voice-grade data.
Transmission and supervisory signaling
A trunk is named for its transmission characteristics. For example, trunks are
always classified by the direction of the traffic they allow:
■ One-way incoming trunk — A local trunk that can be selected (seized) by
the far-end connected switch.
■ One-way outgoing trunk — A trunk that can be seized by the local switch
to call the far-end switch.
■ Two-way trunk — A trunk that can be seized by either of the connected
switches.
Type of trunk Direction
Analog or
Digital? Traffic supported
Transmits
digits?
CO, FX, WATS Incoming
Outgoing
Two-way
Either Any kind of voice or
data traffic.
No
CPE N.A. Either Any kind of voice or
data traffic.
No
DID Incoming Either Only voice and
voice-grade data.
Yes
DIOD Incoming
Outgoing
Two-way
Either Any kind of voice or
data traffic.
Only for
incoming calls
PCOL Incoming
Outgoing
Two-way
Analog
only
Only voice and
voice-grade data.
No
Tie, Access Incoming
Outgoing
Two-way
Either Any kind of voice or
data traffic.
Yes