Technical SpeciÞcations A-15
A
Determining the Distance between the DSU/CSU and the T1 Line Demarcation
Point
You need to determine the correct distance between the DSU/CSU and the T1 line
demarcation point before you connect the T1 cables.
Calculate the T1 transmission loss at the premises remote-end. Transmission loss is
attributed to cable attenuation (signal loss) from the last telephone company repeater
to the DSU/CSU network interface. You do the adjustment with the LBO (L3) which
you set in Menu-4 Main ConÞguration.
1. Actual cable loss depends on the particular cable type and the manufacturer which must
meet AT&T speciÞcation
.
First loss (L1) Phone company loss, between 0 and 22 dB,
speciÞed by phone company
Second loss (L2) Cable length loss. Calculate
L2 from the
distance of the customer premise cabling,
approximately 1dB for every
200 feet
1
(cable
length/200 =dB loss). Cannot exceed
22.5 dB
minus L1
LBO (L3)
DL3900 LBO setting. 15 to 22.5 dB loss
required of the premises remote-end section
(LBO optionsÑ0 dB, 7.5 dB, and 15 dB
down.)
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