Nortel Networks Circuit Card - Manual (Page 50)

Page 50 of 906 Overview
553-3001-211 Standard 3.00 August 2005
Outgoing calls
During outgoing calls from the terminal equipment, a channel is seized when
the station goes off-hook. This simulates a low-resistance loop across the tip
and ring leads toward the lineside T1 card, causing the lineside T1’s receive
A bit to be changed from 0 to 1. This bit change prepares the lineside T1 to
receive digits. Outward address signaling is then applied from the terminal
equipment in the form of DTMF tones or loop (interrupting) dial pulses that
are signaled by the receive A bit pulsing between 1 and 0.
Call disconnect from far end (PSTN, private network or local
Station)
When a call is in process, the central office may disconnect the call from the
CS 1000S, CS 1000M, and Meridian 1. If the lineside T1 port has been
configured with the supervised analog line (SAL) feature, the lineside T1 card
will respond to the distant end disconnect message by momentarily changing
its transmit A bit to 1 and then returning it to 0. The duration of time that the
transmit A bit remains at 1 before returning to 0 depends upon the setting that
was configured using the SAL. If the terminal equipment is capable of
detecting distant end disconnect, it will respond by changing the lineside T1
card's receive A bit to 0 (open loop).The call is now terminated and the
interface is in the idle (on-hook) state.
For the lineside T1 card to support distant end disconnect in loop 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.
• For outgoing trunk calls, the trunk facility must provide far end
disconnect supervision.
• 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 will not provide
battery reversal indication but will only provide a momentary
interruption of the tip ground by asserting the A bit to 1 for the specified
duration.