CXR Larus 80-100-400
Issue 1, July 2006
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CXR Larus 80-100-400
Issue 1, July 2006 1-6
1.222 Each of the output driver cards can select from four inputs, one from each of
the input track and hold cards and one from each DS1, E1, or CC input
reference directly. Logic on each output driver card selects the "best" timing
source. A timing signal from a track and hold card that is tracking an input
reference is "better" than a timing signal from a card that is in holdover. By the
same token, a timing signal from a track and hold card in holdover mode is
"better" than a reference input signal. If at any time a "better" signal source
than the one in use becomes available, the output driver cards will switch to
use the better source. The output driver cards contain circuitry to limit the rate
of output phase change after a switch. The first track and hold card to achieve
tracking mode is selected as the primary card. Circuitry on each output driver
card causes all output cards to select the same timing reference as the
left-most output driver card in the shelf. Most output driver cards produce
twenty output signals each with the exception of Models 54575 and 54577.
1.223 StarClock 200E master shelf can contain auxiliary cards that measure the
performance of the system, provide indication of hardware failures, and furnish
command and status interfaces to the system.
1.224
StarClock 200E provides functional fault tolerance in a number of ways, offering
redundant track and hold cards with dual DS1, E1, or CC inputs and provision
for multiple (up to ten) output driver cards, for example. Since many pieces of
network equipment have two timing inputs, an output from each of two output
driver cards from one StarClock 200E should be connected.
1.225
Another feature is individual DC-to-DC converters on each card. This removes
a common power supply as a single point of failure. Failure of one DC-to-DC
converter affects only one card. Critical components like the track and hold and
output driver cards can be redundant so that a failure of one does not cause a
loss of service in the network equipment.
1.226
Failure of an auxiliary card does not affect the primary system function, which is
to produce accurate timing signals.
1.227 Failures are categorized into major, indicating a loss of service, and minor,
indicating a loss of function. StarClock 200E provides means whereby major
and minor alarms can be connected to indicators to summon service personnel
for timely repair.
