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61280003L2-1B
Section 1 TRACER Description
Line Code
A mark in the data stream is coded as a pulse on the T1 line. A space is coded as "no activity" on the T1
line. As a form of error detection, subsequent marks in the data stream are coded as pulses of alternating
polarity, either positive going or negative going. This type of line coding is called alternate mark
inversion (AMI).
For the T1 receiver to operate correctly, a minimum number of "1s" must exist on the T1 facility. If the
data cannot be guaranteed to meet this requirement, then another line coding format is used. In the
bipolar 8 zero substitution (B8ZS) scheme, a string of eight "0s" is replaced by a special sequence of
eight bits that contains a bipolar violation. The receiver, upon recognizing this sequence, reinserts the
eight "0s" and the data is recovered intact.
DS1/DSX-1 Interface
When connecting the interface to the public switched network, an ADTRAN-provided cross-over cable
(part number 3125M011@A) is required to meet FCC part 68 and IC CS03 requirements. This cable is
required to cross-over the Tx and Rx pairs to meet the connecting arrangement of a network interface
device. This cable is included with the BBP and is labelled "T1 Crossover."
Line Buildout or LBO
The DS1/DSX-1 interface provides two different types of line buildouts (LBOs), respectively. When set
for DS1, LBOs for 0 dB, -7.5 dB, -15 dB, and -22 dB are available. The DS1 interface can operate on
line lengths up to 6,000 feet. When set for DSX-1 interface, LBOs for 0-133 feet, 266-399 feet, 399-533
feet, and 533-655 feet are available.
TRACER SYSTEM CONFIGURATION
A TRACER system is composed of three major subsystems -- a baseband processor, a radio frequency
convertor, and an antenna. The following section describes the system components.
Baseband Processor or BBP
The BBP (ADTRAN part number 1280003L2) is a 1-U, 19-inch rackmountable unit that provides the
system electrical interfaces, user controls and indicators, and performs the spread spectrum processing
for the system. The rear panel provides all of the electrical interface points -- DS1/DSX-1 interface,
DS1/DSX-1 monitor, VT-100 terminal, alarm contacts, IF signal, DC power (from facility), and power
(from AC adapter). The BBP and its rear panel are illustrated in Figure 1-3 and 1-4.
4
T1A
BPV
TEST
LBK
YEL/AIS
POWER
RED
Figure 1-3. BBP
Preliminary
T1B
FREQ
SYSTEM
BPV
LBK
PLAN A
RF LOW
YEL/AIS
PLAN B
LINK DOWN
RED
TRACER 2xT1 User's Manual
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Troubleshooting
