Nortel NT1R20 Description page 66

Page 42 of 290 Description
553-3001-105 Standard 5.00 June 1999
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
Meridian 1. If the line-side T1 port has been configured with the supervised
analog line (SAL) feature, the line-side 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 line-side 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 line-side T1 card to support distant end disconnect in loop start mode,
the following configuration parameters must exist:
— X11 software release 21 or later is required and the Supervised Analog
Line (SAL) feature must be configured for each line-side 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
line-side 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.
— In order to detect distant end disconnect for calls terminating on the
line-side T1 card, the hook flash feature within the SAL software must
be enabled.
— In order to detect distant end disconnect for calls originating and
terminating on the line-side T1 card, both the battery reversal and hook
flash features must be enabled within the SAL software.