Avaya Nortel Communication Server 1000 Reference page 138

NT1R20 Off-Premise Station Analog Line card
The following requirements are based on historic Inserted Connection Loss (ICL)
objectives:
- PBX – CO trunk: 5 dB with gain; 0 – 4.0 dB without gain
- OPS line: 4.0 dB with gain; 0 – 4.5 dB without gain. In recent times economic and
technological considerations led to modifications of these historic objectives. As the
loss provisions in the PBX for OPS are constrained by regulatory requirements as
well as industry standards, they are not designed to compensate for modified ICL
designs in the connecting facilities.
• Nortel recommends that the attenuation distortion (frequency response) of the OPS
facility be within ±3.0 dB over the frequency range from 300 to 3000 Hz. It is desirable
that this bandwidth extend from 200 to 3200 Hz.
• The terminating impedance of the facility at the OPS port be approximately that of 600
ohms cable.
If the OPS line facility loss is greater than 4.5 dB but does not exceed 15 dB, line treatment
using a switched-gain Voice Frequency Repeater (VFR) extends the voice range.
The overall range achievable on an OPS line facility is limited by the signaling range (2300
ohms loop including telephone resistance). The signaling range is unaffected by gain
treatment; so gain treatment can be used to extend the voice range to the limit of the signaling
range. For example, on 26 AWG wire, the signaling range of 2300 ohms corresponds to an
untreated metallic loop loss of 15 dB. Gain treatment (such as a VFR) with 10.5 dB of gain
would maintain the OPS service loss objective of 4.5 dB while extending the voice range to
the full limit of the signaling range.
15.0 dB
– 4.5 dB
= 10.5 dB
The use of dial long line units to extend signaling range of OPS analog line cards beyond 15
dB is not recommended.
Termination transmission characteristics
The loss plan for OPS connections is designed so that a connection with an OPS termination
provides satisfactory end-to-end listener volume when the OPS termination is a standard
telephone. The listener volume at the distant end depends on the OPS termination transmit
loudness characteristics; the volume at the OPS termination end depends on the OPS
termination receive loudness characteristics.
A feature of many (though not all) standard telephones is that the loudness increases with
decreased current. So as the line (PBX to OPS termination) facility gets longer and loss
increases, the increased loudness of the telephone somewhat compensates for the higher
138 Circuit Card Reference
(loss corresponding to the maximum signaling range)
(OPS service loss objective)
(required gain treatment)
Comments? infodev@avaya.com
July 2011