Comdial DXP Plus Series, Руководство пользователя

Страница: 220 / 1176

Installing The Multipurpose Line Board
In The DXP Plus Digital Communications System
1.0 Understanding The Multipurpose Line Board
The Multipurpose line board for the DXP Plus digital communications system provides system interface for
ground start lines, loop start lines, and E&M (tie) lines. These are typically the three different line types that the
central office (CO) makes available for connection to the public switched network. The multipurpose line board is
fully programmable for each type of line.
1.1 Detailing The Line Types
Loop Start Lines: With this line type, the DXP Plus bridges a resistance across the tip and ring leads to signal the
CO to establish a communications link for an outgoing call. The CO detects the resulting current flow and
supplies dial tone to the DXP Plus. The CO signals an incoming call to the DXP Plus by placing an alternating
voltage (ring signal) on the tip lead for the DXP Plus to sense. The DXP Plus then generates ringing to the DXP
Plus station being called. When a station answers the ringing, the circuit is completed as it was for outgoing calls.
Loop start lines can not provide any sure means of determining when a distant party hangs up his or her telephone.
For a system that experiences moderate incoming and outgoing call volume and does not cost calls, loop start
lines provide an economical choice for connecting the DXP Plus to the central office (CO) equipment. When you
use line 1 for the power-fail mode, you must program that line to be a loop-start line unless the industry-standard
telephone that you use as a power-fail station is a ground-start device.
Ground Start Lines: With this line type, the DXP Plus momentarily grounds the ring lead to signal the CO to
establish a communications link for an outgoing call. When the CO detects this, it acknowledges by momentarily
grounding the tip lead. The DXP Plus responds by removing its ground connection and bridging itself across the
tip and ring leads. The CO then removes its ground connection and returns dial tone to the DXP Plus.
For an incoming call, the CO grounds the tip lead and places an alternating voltage on the ring lead for the DXP
Plus to sense. The DXP Plus detects ring-lead ground and then causes its ring generator to generate ringing to the
station being called. When a station answers the ringing, the circuit is completed as it is for outgoing calls.
Because ground start lines are controlled at both ends, they are capable of release supervision that provides a sure
means of determining when a distant party hangs up his or her telephone. This is very important in applications
where calls are costed. Also, since the signalling protocol indicates which end requested the line, it helps prevent
call collisions and glare and thus is useful in applications where there is a high volume of incoming and outgoing
calls occurring on the same lines. Ground start lines are standard protocol for remote networking and are useful
for connecting the DXP Plus to private branch exchange (PBX) equipment. For ground start lines to be
dependable, you must ensure that you have connected the DXP Plus to a low resistance telephone company
ground.
NOTE: The Federal Communications Commission (FCC) requires that you inform the central office that the DXP
Plus is configured as an MF (multipurpose) registered device if you connect it to ground start lines.
E&M Tie Lines: The tie line connections (also known as tie trunk access) are special circuits that allow, on a
dial-up or continuous connection (hot line) basis, the DXP Plus to communicate with remotely located equipment
such as: another DXP Plus, a PBX, or to other common carrier (OCC) equipment for long distance calls. Tie lines
can be a part of a private or leased network and can be metallic, carrier current, T1, or microwave.
R
This manual has been developed by Comdial Corporation (the “Company”) and is intended for the use of its customers and service personnel. The information in this manual is subject to change
without notice. While every effort has been made to eliminate errors, the Company disclaims liability for any difficulties arising from the interpretation of the information contained herein.
The information contained herein does not purport to cover all details or variations in equipment or to provide for every possible contingency to be met in connection with installation, operation, or
maintenance. Should further information be desired, or should particular problems arise which are not covered sufficiently for the purchaser’s purposes, contact Comdial, Inside Sales Department,
Charlottesville, Virginia 22906.
Printed in U.S.A. IMI89-192.01
7/95