DT Etherlink IV
User Manual
- 94 -
6
SERVICE INSTRUCTIONS
6.1
General Requirements
Before unpacking, check if the packing box is intact and if the equipment model is equal to that
specified in the purchase order/contract.
Before running the device, read carefully the present technical description and service
instructions. Take care about all Warnings inside this manual! Remember that the guarantee
and the free-of-charge repair will not be granted under the following conditions:
a) If the device or any of its parts fails due to improper installation, testing or operation.
b) damages resulting from:
1) Misuse and improper installation, including but not limited to:
- to use the product for its normal purpose or in accordance with the all the instructions for
the proper use and maintenance,
- installation and use of the product in a conflicting way with the actual technical or safety
standards in the country where it is installed, as well as the connection of the device to any
other power supply source, that fulfil the required technical or safety standards.
2) Maintenance or repair performed by unauthorized service centers and dealers.
3) Operation of a malfunctioning device.
4) Accidents, lightning strokes, flooding, water, fire, improper ventilation, voltage drops,
ingress of moisture and insects inside the equipment as well as other reasons, for example,
electromagnetic and other interferences which are beyond the supplier control and do not
correspond to specified technical conditions.
5) Transportation except when the shipping is performed by an authorized dealer or a
service center.
7) Defects of the system into which this product is included.
If the equipment should be powered from a primary DC source (38
… 72 V), please us it with
the grounded “+”.
Environment requirements: Temperature: from -5 to +45
°C
; Relative air humidity: from 5% to
85% at +25
°C
. Exceptions are units that are specified from the manufacturer to differ from
these requirements, because there is a special application.
It is strictly prohibited:
a) to alter, delete, remove or make illegible the serial number of the device.
b) to adapt, adjust and change the equipment in order to improve it or extend its applications
without the prior written consent of the manufacturer.
c) to alter or to adjust the equipment without the consent of the manufacturer.
6.2
Evaluation of the Digital Channel Quality and Operation Parameters
The digital channel quality is evaluated by:
The ITU-T Rec. G.826 error performance (G826) monitoring of a SHDSL link is performed
according to ITU-T Rec. G.704, based on CRC (Cyclic Redundancy Check) error detection.
Six CRC6 check bits are generated per SHDSL frame. CRC6 errors are used by the software
to count the block errors of the SHDSL channel.
The Noise Margin (NM) performance monitoring.
The Noise Margin (NM) provides qualitative performance information of a specific SHDSL link
according the ITU-T Rec. G.991.2. The <NM> command is used to show the noise margin. The
recommended NM values should be no less than 6 dB. This value provides the necessary reserve of
the signal/noise margin. It is recommended to perform the Noise Margin performance monitoring
during acceptance tests and in case the system operates not stable. The test is also used to locate
any damaged cable segment
.
In addition, it is also recommended to monitor regularly the quality of data transmission over E1
interfaces. On the E1 side, four CRC4 check bits are generated per sub-multiframe (SMF) and
