Nortel Networks 553-3001-211 manual Outgoing calls

Page 48 of 894 Overview

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.

553-3001-211 Standard 2.00 September 2004