Symmetricom SDU-2000, User Manual

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Output Module Reference Data
2048 kHz Output Module
192 SSU-2000 User’s Guide 12713020-002-2 Revision D – April 2004
2048 kHz Output Module
This section provides reference data for the 2048 kHz Output module (part number
23413159-000-0). It also contains default provisioning settings, and procedures for
connecting to the SSU-2000 in order to enable, provision, and disable the module.
Functional Overview
The 2048 kHz Output module receives a set of three (four if installed in an
expansion shelf) 4 kHz clocks from the Clock modules and uses these clocks to
develop an 8.192 MHz phase-locked signal. This phase-locked signal is then used
to generate 20 sets of 2048 kHz clock outputs.
The 20 sets of 2048 kHz signal pairs TTIP and TRING represent a
transformer-coupled symmetrical pair. Each output can be turned on/off
independently of other channels; relays on each output allow for disconnecting the
driver output from the output pins. Each output signal is monitored for a failed output
on an independent basis. An output signal is designated failed when the level falls
below 0.75 volts base to peak.
In non-redundant configuration a failed output will not be turned off, as some
equipment may tolerate a wide range of level and still be operating. In redundant
operation a failed output will be turned off in one module at a time to try and isolate
the source of the problem. The outputs meet the criteria set forth in ITU-T G.703 for
signal type, amplitude, and waveshape.
Output Squelching
A new feature, available with Revision C of the firmware for the 2048 kHz Output
module, allows you to selectively turn off (squelch) the outputs during periods of
degraded performance. To use this feature, the Communications module must have
Revision D or later firmware.
This feature allows you to turn off any of 20 output ports on redundant or
non-redundant modules. The SSU-2000 uses the system Priority Quality Level
(PQL) to determine when the system is operating within specified limits; if the
outputs become degraded, then the system automatically turns off the affected
ports.
To enable the squelching feature, you must provision a “threshold” PQL value using
the ICS OUTPUT command or the TL1 SET-PRMTR-CLKOUT command. A
threshold PQL value of zero disables the squelch function. Threshold PQL values
above zero enable the squelch function; when the system PQL is greater than the
threshold PQL, the output is squelched.