ADC HDSL4 Manual do Utilizador descarregar pdf (Página 37)

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Single or multi-gauge ( 19, 22, or 24 ) cable plus bridged tap may not exceed 12 kft

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HDSL2 requires that Multi-gauge containing 26-gauge cable plus bridged tap may not exceed 9 kft. This

conforms to Carrier Serving Area Guidelines (Loop Deployment Policy and Guidelines, Section 4.1.1, 9/00).

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EML - Engineered/Estimated Measured Loss; The engineering approximation of loss on a loop using Carrier

Serving Area ( CSA ) design rules ( 35 < dB depending on local guidelines ) for an HDSL span. This is an estima-

tion of the AML, but takes into consideration the quality of the plant, environmental temperature fluctuation, record

inaccuracies, BT and gauge changes.

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FEXT - Far-End X-Talk(crosstalk). A type of crosstalk which occurs when signals on one twisted pair are coupled

to another pair as they arrive at the far end of multi-pair cable system. FEXT is an issue on short loops supporting

high-bandwidth services such as VDSL (Very-high-bit-rate Digital Subscriber Line), given the relatively high carri-

er frequencies involved. Services such as ADSL and HDSL are not affected to the same extent, as the loops are

longer and as such interference tends to be attenuated (weakened) on longer loops.

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NEXT - Near-End X-Talk. A type of crosstalk which occurs when signals transmitted on one pair of wires are fed

back into another pair. Since at this point on the link the transmitted signal is a maximum strength and the receive

signal has been attenuated, it may be difficult to maintain an acceptable ACR (Attenuation-to-Crosstalk Ratio).

NEXT is particularly troublesome when a number of high-speed transmission services (e.g., ADSL, HDSL and T-

carrier) are supported within a single copper cable system. Shielded or screened cable systems are more desir-

able in addressing this problem than are unshielded varieties.

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PA - Pulse Attenuation; The HDSL equipment measured loss on all sections in a HDSL designed span ( 28 to 30

dB max depending on the manufacturer ). This PA reading must be determined by using a laptop or dumb termin-

al at the RS232 jack of the HDSL unit.

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· Adtran = 30 dB (HTU-C/HTU-R)

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· Pair Gain Technologies = 28 dB (HLU/HRU)

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· ADC HDSL Loop Extender Shelf = 31dB (HLXC/HLXR)

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SNR - Signal to Noise Ratio; The ratio of the usable signal being transmitted to the noise or undesired signal.

Usually expressed in decibels. This ratio is a measure of the quality of a transmission. The signal to noise differ-

ence is measured by the HDSL equipment and using a laptop or dumb terminal at the RS232 jack to get the

reading.

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SR - Sync Readings; Loss of synchronization between HDSL units as measured by the HDSL equipment using a

laptop or dumb terminal at the RS 232 jack on the HDSL units

9. Attachment 4 - HDSL Remote Unit Problems

4.1 A study was done on returned HDSL remote units.

AT&T Practice ATT-TP-000-000-006

Issue 1, 08/25/06

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