Page 2-86
Specifications
INTER-TEL
®
AXXESS
®
MANUAL VERSION 11.0 – May 2008
Off-Premises Extensions (OPX)
N. OFF-PREMISES EXTENSIONS (OPX)
5.70 An OPX is an AC ringer-equipped single-line DTMF set that is placed in a remote loca-
tion and connected to the system through a telephone company [network provider in Europe]
OPX circuit or a customer-provided circuit.
5.71 The circuits are connected using Single-Line Adapter (SLA) circuits, which are con-
nected to available Digital Keyset Card (DKSC) and/or 16-Port Digital Keyset Card (DKSC-
16) circuits. OPX circuits can also be connected using T1/E1 circuits, which are connected to
available T1, E1, T1/PRI or E1/PRI card circuits.
NOTE: OPXs do not support visual message waiting applications. If single-line sets with mes-
sage waiting lamps are installed as off-premises extensions, the lamps do not function. How-
ever, single-line sets can be configured in DB Programming to receive audible message waiting
indication tones.
5.72 With a U.S. system, the OPX circuits provided by the telephone company are identified
with Facility Interface Codes (FIC): Class A, OL13A; Class B, OL13B; or Class C, OL13C.
The service order code is 9.0F (fully protected private circuit). If the impedance does not
exceed a loop measurement of 800 ohms (loop of 15,600 feet (52 km) using 24AWG (0.6 mm)
wire), a customer-provided circuit between the remote location and the system may be used.
5.73 With a Europe system, the OPX circuits are either provided by the network provider, or,
if the impedance does not exceed a loop measurement of 800 ohms (loop of 15,600 feet/4754
m. using 0.5 mm. wire), a customer-provided circuit between the remote location and the sys-
tem may be used.
5.74 The 800-ohm loop limitation is usually suitable for accessing on-premises stations from
off-premises stations. However, for applications where one off-premises station is calling
another through the station card, the impedance between the two off-premises stations (both
circuits added together) must be less than 800 ohms (loop measurement). With a U.S. system, a
Class A or B FIC circuit is preferable.
5.75 When an SLA circuit is designated for OPX use in DB Programming (see page 6-118),
its voice volume levels are increased approximately 3dB over normal single-line set voice vol-
ume levels. This is an attempt to compensate for any loss in the external OPX circuit. How-
ever, in certain off-premises applications, the voice volume levels may still be unacceptable.
This degradation in voice volume is due to the natural voice frequency range limitations of the
telephone company [network provider in Europe] or customer-provided circuit. To increase the
frequency range, installation of a two-wire, negative impedance repeater unit is recommended.
Such units typically provide from 0-15 decibels of voice volume gain and allow regulation of
the gain in each direction when simultaneous voice transmission occurs. The switching sensi-
tivity on the unit should also be adjustable.
5.76 The repeater unit is installed at the MDF between the station block and the cabling to
the off-premises station. (See page 3-69 for OPX installation instructions.) When ordering a
repeater unit, consult with the supplier for ordering the proper mounting shelf and power sup-
ply for the unit. Additional information on operating and adjusting the repeater unit is gener-
ally included with the product.
NOTE: Each OPX circuit can have extended ring cadence enabled or disabled (see page 6-
211). The extended setting lengthens the duration of the ring signal to meet the requirements of
many OPX and/or repeater applications. The default setting is disabled.
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