Lucent Technologies 8.2

DEFINITY ECS Release 8.2

Administrator’s Guide

555-233-506 Issue 1

April 2000

Features and technical reference

1570Trunks and Trunk Groups

■Start-dial signal — The distant office’s acknowledgment that it is ready to

accept dialing from the originating office.

Seizure signals

Ear & Mouth (E&M) supervision

E&M supervision is a symmetric signaling scheme used on private network

trunks. DC voltage levels are sent over E&M leads, which are separate from the

transmission path. E & M signals indicate on-hook and off-hook states for each

end of the connection path.

Ear & Mouth (E&M) supervision on digital trunks

DIOD trunk groups support Continuous and Pulsed E&M Signaling that allows

you to make and receive calls over Brazil pulsed or continuous E&M signaling

trunks and Hungarian pulsed E&M signaling trunks. Refer to DEFINITY ECS

Application Notes for Type Approval for more information.

Ground-start (GS) supervision

Ground-start signaling is a supervisory signaling scheme used on public network

trunks in which ground is applied on the tip (T) lead by the CO and on the ring (R)

lead by the switch. For example, the calling switch on a call to a CO seizes the

outgoing trunk by placing a ground on the trunk interface R lead. The CO

recognizes the trunk seizure as a request for service and grounds the trunk T lead

to indicate to the calling switch that the CO is ready to receive digits. Gro und-star t

signaling is superior to loop-start signaling (described below) for the following

reasons:

■The switch can make trunks busy to outgoing calls almost immediately,

because the tip ground seizure by the distant switch minimizes the interval

during which a two-way trunk can be seized from both ends (called glare).

■Ground-start signaling allows answer supervision, a positiv e indication th at

a distant switch has disconnected from a call. Answer supervision has 2

benefits:

— Callers who remain off-hook after completing a call won’t be

connected to central office dial tone. For example, this prevents a

restricted station from making an unauthorized call after placing an

authorized call using the attendant.

— By holding the trunk busy until the central office disconnects,

another switch cannot seize the trunk and be connected to the CO

party of the previous call.