Document 180-0178-001 R03
IMPORTANT NOTE: The BRX-XLR unit is powered from the Sealing Current
found on a standard POTS pair. Each pair of the BRX-XLR-24 is powered
independently with each pair requiring the presence of the -48Vdc sealing
current for proper operation. The BRX-XLR-24 will not operate on a dry pair
(line with no -48Vdc sealing current). You can use the Positron BRX Power
Injector to provide the -48Vdc sealing current when operating on dry pairs.
Connecting the BRX-XLR-24
Step 1: Select the location where the BRX-XLR-24 will be inserted using the
BRX Cloud Calculator for the longest loop.
Step 2: Connect the grounding lug of the unit to a proper ground (usually
available near the splice point).
Step 3: Insert a BRX-BYPASS-TEST module in slot 1 and ensure that both
switches are in BYPASS mode.
Step 4: Connect the rst two (2) pairs to be amplied to the rst two (2) pairs of
the BRX-XLR-24. Make sure to match the DSLAM pair number to the CPE pair
number.
Step 5: Test for continuity between the DSLAM pair and CPE pair at the splice
point. If the circuits are active, the LEDs on the BRX-BYPASS-TEST module will
be ON to conrm that the sealing current is present on both lines. If either circuit
is not active, the continuity testing will conrm that the connections are reliable.
Step 6: Replace the BRX-BYPASS-TEST module with a BRX-XLR-M module.
Step 7: The DSLAM and CPE will now retrain the circuit and bring up the
ADSL2+ / ADSL link with the amplied bandwidth. The performance may be
limited (or capped) by a setting in the DSLAM conguration.
Step 8: Repeat steps 3 to 7 for the other eleven (11) slots of the BRX-XLR-24
enclosure.
Placement Guidelines for BRX-XLR Devices
The BRX-XLR amplies ADSL2+ and ADSL loops and is designed to deliver
solid amplication of the loops as long as the BRX-XLR device is installed within
45% to 75% of the total loop distance. It is recommended to install the BRX-
XLR unit at an existing splice point that is within the recommended placement
range. When multiple splice points exist within that range, you should select the
one that is most convenient.
The BRX-XLR installation should follow these simple rules:
1. L1 - Minimum Loop Length from DSLAM to BRX-XLR should be
no less than 6500 feet (2 km) for 24 AWG (0.5 mm) gauge or 5000 feet
(1.5 km) for 26 AWG (0.4 mm) gauge.
2. L2 - Minimum Loop Length from CPE to BRX-XLR should be no less than
650 feet (200 m) for 24 AWG (0.5mm) gauge or 500 feet (150 m) for 26 AWG
(0.4 mm) gauge.
For a 10 / 1 Mbps service, the recommended range is as follows (single pair):
• Maximum total loop length: 17500 feet (5.3 km) for 24 AWG (0.5mm)
gauge or 12750 feet (3.9 km) for 26 WG (0.4 mm) gauge.
• Recommended placement range: 8000 to 12000 feet (2.4 to 3.6 km) of
24 AWG (0.5mm) gauge or 5700 to 8900 feet (1.7 to 2.7 km) of 26 AWG (0.4
mm) gauge.
The BRX Cloud Calculator can help determine the optimal installation
location for each specic loop. To access the BRX Cloud Calculator, sign up
on the Positron Access Portal at www.positronaccess.com/Portal.php.
You will get a username and password to access the Portal.
Recommended DSLAM Settings
Parameter Downstream Upstream
Maximum Bitrate 32000 kbps 1296 kbps
Maximum Delay 8 msec 8 msec
Path Latency Interleaved
Impulse Noise Protection (INP) 2 1
Target SNR Margin 6.0 dB 6.0 dB
In order to fully benet from the amplied ADSL2+ / ADSL signal, there are a few
DSLAM settings to be set as per the following recommendation:
You should also make sure that the DSLAM and/or the BRAS settings are not set at
a lower level than the target service offered to the subscriber for this loop.
NOTE: You should always follow your corporate guidelines for the DSLAM
settings if they differ from the Positron recommendation. If in doubt, you should
check with the Engineering or Operation team.
Summary Diagram of Typical Installation
DSLAM BRX-XLR-24
L1
Distance from DSLAM to BRX-XLR-24
L2
Distance from BRX-XLR-24 to CPE
CPE
