Nortel Networks 311

Application 159

A feature of many (though not all) standard telephones is that the loudness

increases with decreased current. So as the line (Meridian 1 to OPS

termination) facility gets longer and lossier, the increased loudness of the

telephone somewhat compensates for the higher loss, assuming direct

current feed from the PBX with constant voltage at the feeding bridge.

However,this compensation is not available when:

•the termination is a non-compensating telephone

•the OPS port is served by a line card using a constant-current feeding

bridge

•the OPS termination is to telephones behind a local switch providing

local current feed, such as a fax machine

OPS line terminations with loudness characteristics designed for other

applications can also impact transmission performance. For example,

wireless portables loudness characteristics are selected for connections to

switching systems for wireless communication systems; if used in an OPS

arrangement without consideration for these characteristics, the result could

be a signiﬁcant deviation from optimum loudness performance.

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 set. 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.

On some standard telephone sets, the loudness increases with decreased

current. As the line (PBX to OPS termination) facility gets longer and loss

increases, the increased loudness of the set compensates for the higher

loss, assuming direct current feedfrom the PBX with constant voltage at the

feedingbridge. This compensation is not availablein the following situations:

•when the termination is a non-compensating telephone set

•when the OPS port is served by a line card using a constant-current

feeding bridge

•when the OPS termination is to telephone sets behind a local switch

providing local current feed, such as a key telephone system

OPS line terminations with loudness characteristics designed for other

applications can also impact transmission performance. For example,

wireless portables loudness characteristics are selected for connections to

switching systems for wireless communication systems; if deployedin an

OPS arrangement without due consideration for these characteristics, the

result could deviate signiﬁcantly from optimum loudness performance.

Nortel Communication Server 1000

Circuit Card Reference

NN43001-311 01.04 Standard

Release 5.0 23 May 2008