Analog Line Call Operation - Avaya Nortel Communication Server 1000 Reference

from the controller and return incoming call status information to the controller over the DS-30X
network loop.

Analog line call operation

The applications, features, and signalling arrangements for each line interface unit are
configured in software and implemented on the card through software download messages.
When an analog line interface unit is idle, it provides a voltage near ground on the tip lead and
a voltage near –48 V dc on the ring lead to the near-end station. (The near-end station is the
telephone or device that is connected to the analog line card by the tip and ring leads.) An on-
hook telephone presents a high impedance toward the line interface unit on the card.
Incoming calls
Incoming calls to a telephone that is connected to an analog line card can originate either from
stations that are local (served by the PBX), or remote (served through the Public Switched
Telephone Network (PSTN)). The alerting signal to a telephone is 20 Hz (nominal) ringing.
When an incoming call is answered by the near-end station going off-hook, a low-resistance
dc loop is placed across the tip and ring leads (towards the analog line card) and ringing is
tripped. See
page 44.
Outgoing calls
For outgoing calls from the near-end station, a line interface unit is seized when the station
goes off-hook, placing a low-resistance loop across the tip and ring leads towards the analog
line card. See
When the card detects the low-resistance loop, it prepares to receive digits. When the system
is ready to receive digits, it returns dial tone. Outward address signaling is then applied from
the near-end station in the form of loop (interrupting) dial pulses or DTMF tones.
Circuit Card Reference
Figure 6: Call connection sequence - near-end station receiving call
Figure 7: Call connection sequence - near-end originating call
Line cards
on
on page 45.
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