Administrator's Guide

Features and technical reference

555-233-5061912 Issue 5 October 2002

Digital trunks represent both sound and data as 0’s and 1’s and can be configured

to carry any kind of voice or data traffic. Digital trunks connect to a DS1 circuit

pack and provide a T1 or E1 carrier. DS1 service provides an interface for CO,

FX, DID, tie, and WATS trunks. The DS1 interface supports incoming and

outgoing dial types of ground-start, loop-start, auto/auto, auto/delay, auto/immed,

and auto/wink. Signaling may be robbed-bit or common-channel depending on

the trunk type and whether the dial-type is incoming or outgoing. The interface

may be used to connect the switch to a toll office directly using wink-start tie

trunks for two-way access to the toll network.

Supervision, addressing, and alerting methods have been carried over to digital

trunks, which use basically the same signaling scheme as analog trunks when

establishing a call. These schemes are handled in a variety of ways to indicate

particular calling states, such as on-hook, off-hook, ringing, not ringing, and so

on, by using A and B bit-timed signaling. A and B bits carry a 0 or 1 depending on

the type of trunk, the near-end channel unit type, far-end channel type, the

condition of the trunk (open loop, loop closure, reverse battery, and so on), and

whether it is transmit or receive signaling. In addition to the above, see ‘‘DS1

Circuit Pack’’ on page 757 for trunk-related terms associated with DS1 trunk

interfaces.

Interactions

■ Brazil Block Collect Call

In both continuous and pulsed E&M signaling, Block Collect Call is not

included.

■ Personal Central Office Line (PCOL)

PCOL trunks cannot use continuous, pulsed, or discontinuous E&M.