Ground start restrictions – Nortel Networks 1000 User Manual

Page 42

Overview

Table 4
Ground Start Call Processing A/B Bit Settings (cont’d.)

Transmit

Receive

State

•

Terminal equipment goes open loop current

•

Lineside T1 card opens tip ground

Ground Start Restrictions

If the Lineside T1 card is used in ground start mode, certain restrictions
should be considered. Because the system treats the Lineside T1 card as
a standard loop start analog line card, the ground start operation of the
Lineside T1 card has operational limitations compared to typical ground
start interface equipment relating to start of dialing, distant end disconnect
and glare potential.

Distant end disconnect restrictions

If the SAL feature is not available

in the CS 1000 software, the Lineside T1 card is not capable of indicating
to the Customer Premise Equipment (CPE) when a call is terminated by
the distant end. In this case, the Lineside T1 card continues to provide
a grounded tip indication (A=0) to the CPE until it detects an open loop
indication (A=0) from the CPE, at which time it provides an open tip
indication (A=1). Therefore, without SAL software, the Lineside T1 card is
not capable of initiating the termination of a call to the CPE.

With the SAL software configured for each Lineside T1 line, the Lineside
T1 card provides an open tip indication to the CPE when it receives an
indication of supervised analog line from the system. This provides normal
ground start protocol call termination.

Glare restrictions

In telephone lines or trunks, glare occurs when a

call origination attempt results in the answering of a terminating call that
is being presented by the far end simultaneously with the call origination
attempt by the near end.

The Lineside T1 detects presentation of a terminating call (outgoing to
Lineside T1 terminal equipment) by detecting ringing voltage. If application
of the ringing voltage is delayed due to traffic volume and ringing generator
capacity overload, the Lineside T1 ground start operation cannot connect
the tip side to ground to indicate the line has been seized by the system.

In ground start mode, glare conditions need to be considered if both
incoming and outgoing calls to the Customer Premise Equipment (CPE)
are going to be encountered. If the system and the CPE simultaneously

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311

02.06

Standard

27 August 2008