ADTRAN 3192 H4TU-C, Установка и эксплуатация

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20 Issue 1, December 2003 61223404L2-5A
7. Resistance Values. See Table 9 .
Each of the three segments associated with span
powering two H4Rs and a H4TU-R must satisfy
the DC resistance budgets in addition to the
recommended loop attenuation requirements. In
general, 22 and 19 AWG segments will be
restricted by their loop attenuation while the DC
resistance will restrict the segment reach for 26 and
24 AWG. When designing a dual H4R loop, the
first segment should have lower DC resistance than
the second segment.
Single H4R spans do not require any restriction
due to DC resistance.
NOTE
A circuit that otherwise meets attenuation and
other requirements for cable reach will
encounter span powering problems if resis-
tance values are excessive.
The segment resistance (
Ω
segment
) is determined using
this equation:
Ω
segment
= L
26
*
Ω
26
+ L
24
*
Ω
24
+ L
22
*
Ω
22
+ L
19
*
Ω
19
where L
#
is the length of # AWG cable (kft., excluding
bridged taps) and
Ω
26
is the DC resistance of #AWG cable.
Note: Interpolated between 70
°
F and 120
°
F data. Extrapolated from 70
°
F and 120
°
F data.
Table 9. Single Pair DC Resistance Value
Resistance (ohms/kft)
AWG 70°F 90°F 120°F 140°F
19 16.465 17.183 18.261 18.979
22 33.006 34.446 36.606 38.046
24 52.498 54.789 58.225 60.516
26 83.475 87.117 92.581 96.223