Meridian Nortel 1 Option 11C Technical Reference Manual page 436

Page 436 of 544
553-3011-100 Standard 14.00
NT1R20 Off Premise Station (OPS) analog line card
The overall range achievable on an OPS line facility is limited by the
signaling range (2300 ohm loop including telephone set resistance). Signaling
range is unaffected by gain treatment; thus, 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 dB (loss corresponding to the maximum signaling range)
• – 4.5 dB (OPS service loss objective)
• = 10.5 dB (required gain treatment)
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 will provide 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;
that at the OPS termination end depends on the OPS termination receive
loudness characteristics. With standard telephone sets, these characteristics
are such that satisfactory—if not optimum—performance is achievable
within the above noted objectives for connecting facilities.
A feature of many (though not all) standard telephone sets is that the loudness
increases with decreased current. Thus, as the line (Meridian 1 to OPS
termination) facility gets longer and loss increases, the increased loudness of
the set 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 set
• the OPS port is served by a line card using a constant-current feeding
bridge
• the OPS termination is to telephone sets behind a local switch providing
local current feed, such as a key telephone system
January 2002