Operation; Incoming Calls - Meridian Nortel 1 Option 11C Technical Reference Manual

NT1R20 Off Premise Station (OPS) analog line card Page 429 of 544

Operation

The applications, features, and signaling arrangements for each unit on the
OPS analog line card are assigned through the Single-line Telephone
Administration program (LD10) and/or jumper strap settings on the card.
The operation of each unit is configured in software and is implemented in
the card through software download messages. When the OPS analog line
card unit is idle, it provides a ground on the tip lead and – 48 V dc on the ring
lead. The on-hook telephone presents a high impedance toward the line
interface unit on the card.

Incoming calls

Incoming calls to a telephone connected to the OPS analog line card originate
from stations that can be local (served by the Meridian 1 PBX) or remote
(served through the public switched telephone network). The alerting signal
to telephones is 20 Hz (nominal) ringing. When an incoming call is answered,
ringing is tripped as the telephone goes off-hook, placing a low-resistance DC
loop across the tip and ring leads towards the OPS analog line card (see
Table 134 on page 430).
Option 11C and 11C Mini Technical Reference Guide