2-14 Overview
SG 2000 Installation and Operation Manual
Level Control
The gain of hybrid IC amplifiers varies with temperature. In addition, changes in system channel
loading and/or splices in the fiber link can change the level of the received signal.
The standard TCU board compensates for anticipated hybrid gain changes by sensing housing
temperature and signaling needed changes to the RF attenuator.
The ADU board, an optional plug-in module, monitors the amplitude of a selected pilot frequency.
The pilot frequency is an available analog television channel not scrambled by the sync suppression
method. Any changes in amplitude are fed back to the RF attenuator that makes appropriate
corrections.
The input to the ADU contains a JXP-* pad. The factory-installed value of this pad is 6 dB (JXP-6)
for bridger level outputs and 0 dB (JXP-ZX) for trunk level outputs. Under normal conditions, it
should not be changed.
Options and Accessories
Table 2-3 provides a list of options and accessories for the SG 2000:
Table 2-3
Options and accessories
Model Description Function
ADU-*
Automatic drive
unit
This option automatically adjusts gain by monitoring changes
in the level of the selected pilot carrier. Either an ADU or TCU
must be installed.
TCU
Thermal control
unit
The TCU controls amplifier gain for changes in hybrid gain at
the sensed temperature.
JXP-*A
Fixed
attenuator
Attenuator pads are used to adjust amplifier levels and are
available in 1 dB steps from 1 through 24 dB. The appropriate
value must be installed.
JXP-ZX
0 dB attenuator This attenuator is used in place of JXP-*A pads when no
attenuation is needed.
FTEC
Crowbar
overvoltage
protection
The FTEC is an electronic crowbar/surge protector that can be
used to replace the existing 230-volt gas discharge surge
protector.
LL-SG2
LIFELINE
module
This module enables the system operator to monitor the SG2
from a remote location. See Section 5, “Operation” for
parameters monitored. Several frequencies are available. See
the product catalog for additional information.
GFAL
Test probe This probe is used to evaluate node performance.
F/JXP
Injection probe This probe is used to inject a signal for test purposes.
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