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162 TimeHub 5500 User’s Guide
097-55501-01 Revision M – January 2009
Chapter 4 Testing and Configuring the TimeHub
Provisioning Inputs on a Master Shelf
To change the MONITOR setting, click the Monitor check box for the desired input.
4. Set the PRS Input frequency, if needed. The PRS reference frequency can be
set to expect either a 5 or 10 MHz input. The default is 10 MHz. If necessary,
change the setting.
Use the control labeled
PRS Frequency
in the lower right of the Configuration
Input tab to set the PRS frequency.
5. Change priorities if desired. The priority setting provides a way to prefer a
particular input for use as the active timing reference when more than one input
has been qualified. The lower the number, the higher the priority. The default is
that the PRS input has highest priority and all others are equal. If you want DS1
input 2 to be preferred over DS1 input 1, lower the input 2 priority or raise the
input 1 priority.
Use the
Priority
row on the Configuration Input tab to change the priority of the
selected input as desired.
6. Set Framing for enabled DS1 inputs, if needed. DS1 inputs may have either D4
(also known as SF) or ESF framing. TimeHub defaults DS1 inputs to expect D4
framing, so if you have ESF inputs the setting needs to be changed.
Use the
T1 Framing
row on the Configuration Input tab to set the framing of
selected input as appropriate.
7. Set Bridged mode for enabled DS1 inputs, if needed. Generally, DS1 inputs
connected to TimeHub will be terminated at the input. However, if the reference
signal is bridged (which means it will be nominally 20 dB lower in amplitude), the
bridged selection should be set for any such input. The default setting is that
bridged inputs are not expected for inputs 1 – 4.
Use the
BRIDGED
row on the
Configuration
,
Input
tab to change the setting
for any appropriate inputs.
8. Configure inputs to use SSM, if desired. If ESF-framed DS1 inputs contain SSM
messages that you want to use as part of the input qualification process, follow
steps 9 and 10 to enable the SSM capability. The default is that SSM is not used
for qualifying inputs. If you do not want to use SSM for input qualification,
continue at
On the Configuration Input tab, select
SSM
to use SSM as an input qualification
criteria. Selecting
Without SSM
causes the TimeHub to ignore SSMs as a
consideration for input qualification.
9. Enable SSM reading for ESF-framed DS1 inputs. Inputs that are incapable of
SSM decoding (such as PRS or D4-framed DS1) use an assumed SSM value
(see keyword QLEVEL in the TimeHub 5500
TL1 Reference Manual
). The
ESF-framed DS1 inputs will also use an assumed value unless reading of SSM
is enabled.