12778474-002-2 Revision F – March 2004
TSG-3800 User’s Guide 209
Output Modules
AMI 20-Output Module
Rocker switch S1 and MUX 2 control the selection of the A/B clock pair used by the
module to generate its outputs. When the CLKSEL switch is On, MUX 2 selects the
CLK1 inputs. When it is Off, the CLK2 inputs are selected.
A third rocker switch in S1, labeled TCLKSEL, configures the output drivers for the
frequency of the clock selected by MUX 2. When this switch is Off, the drivers are
configured for a clock of 1.544 MHz (T1); when the switch is On, the drivers are
configured for 2.048 MHz (E1).
The shape of the output waveform is controlled by the output drivers and by the
three remaining switches in S1, labeled LEN0, LEN1, and LEN2 (TCLKSEL = On),
that are connected to the drivers. Depending upon the settings of these switches,
the output drivers will produce the appropriate output pulse shape to meet the
DSX-1 or CSU templates over a wide variety of cable types and lengths.
When TCLKSEL is Off, the E1 mode is enabled. In this mode only one output pulse
shape is available. LEN0, LEN1, and LEN2 may be in any state, except all On. A
safe setting for these three switches is Off.
MUX 3 selects either the A input and A clock (default) or the B input and B clock
from the input and clock pairs selected by MUX 1 and MUX 2. These signals are
used by the output buffers to generate the desired outputs.
If the A input or A clock fails, the module detects this and switches to the B signals
automatically. The amber INPUT FAULT A indicator is turned on and the CPU is
notified. The module continues to operate from the B inputs with a fault indicated
until it is replaced or the A inputs return. If the A inputs return, the module
automatically switches back to them. This is the preferred operating condition.
A failure of the B signals causes the module to turn on the amber INPUT FAULT B
indicator and to notify the CPU module. There is no automatic switchover to the A
inputs, because the module will already be using them if they are good. The module
can be made to change its reference through the CPU module.
The module checks the outputs to confirm signal presence. If an output fails, the
OUTPUT FAULT indicator (red) on the front panel is turned on. The CPU is also
informed of this condition through the Frame Generator module. The relay through
which the output is connected to the rear panel is de-energized, disconnecting the
failed output on this module from the corresponding output on the backup module.
When an output fails, there may be a temporary loss of the corresponding signal on
the backup module. However, this is cleared automatically within one second, when
the CPU attempts to clear the faults generated by both modules. The other outputs
are not affected.
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