Nortel Networks 1000 - Manual (Page 40)

40 Overview
Incoming Calls Incoming calls to terminal equipment that is connected
to the Lineside T1 card can originate either from stations that are local
(served by the PBX), or remote (served through the public switched
telephone network). To provide the ringing signal to the terminal
equipment the Lineside T1 card simulates the 90V ring signal on the ring
lead by alternating the transmit B bit between 0 and 1 (0 during ring on,
1 during ring off), and ground on the tip lead by setting the transmit A
bit to 0. When an incoming call is answered (by the terminal equipment
going off-hook), the terminal equipment simulates tripping the ringing and
shutting off ringing by causing the lineside T1’s receive A bit to change
from 0 to 1. The Lineside T1 card responds to this message by simulating
loop closure by holding the transmit B bit constant at 1.
Outgoing Calls During outgoing calls from the terminal equipment, a
channel is seized when the terminal equipment goes off-hook, simulating a
ground to the ring lead toward the Lineside T1 card by causing the lineside
T1’s receive B bit to change from 1 to 0. In turn, the Lineside T1 card
simulates grounding its tip lead by changing the transmit A bit to 0. The
terminal equipment responds to this message by removing the ring ground
(lineside T1’s receive B bit is changed to 1) and simulating open loop at
the terminal equipment (lineside T1’s receive A bit is changed to 0).
Call disconnect from far end PSTN, private network or local
station
While a call is in process, the far end might disconnect the call.
If the Lineside T1 port has been configured with the Supervised Analog
Line (SAL) feature, the Lineside T1 responds to the distant end disconnect
message by opening tip ground. This causes the Lineside T1 card to
change the transmit A bit to 1. When the terminal equipment sees the
transmit A bit go to 1, it responds by simulating open loop causing the
lineside T1’s receive A bit to change to 0. The call is terminated and the
interface is once again in the idle condition.
For the Lineside T1 card to support distant end disconnect in ground start
mode, the following configuration parameters must exist:
• The Supervised Analog Line (SAL) feature must be configured for each
Lineside T1 port.
Note: By default, the SAL feature opens the tip side for 750 m/s in
loop start operation. This is configurable in 10 m/s increments.
•
In order to detect distant end disconnect for calls originating on the
Lineside T1 card, the "battery reversal" feature within the SAL software
must be enabled. Enabling the battery reversal feature does not
provide battery reversal indication when a call is answered; it only
provides battery reversal indication when a call is disconnected.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 02.06 Standard
27 August 2008
Copyright © 2003-2008 Nortel Networks
.