Symmetricom XLi IEEE 1588 User Manual

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The XLi responds:

To set a new Power-On Alarm Suppress value, enter the following string, replacing <SEC> with the 
number of seconds 

(Range 0 to 86,400 seconds)

, enter:

The XLi responds:

OK<CR><LF>

Use function F74 to select the primary and secondary reference sources and configure the fail-over 
sequences. The switching modes are:

•

PRI or “Primary”: Ensures the unit remains connected to the primary source and doesn’t attempt 

to switch. PRI is the factory setting.

•

SEC or “Secondary”: Ensures the unit remains connected to the secondary source and doesn’t 

attempt to switch.

•

PRI – SEC – SEC or “Primary – Secondary – Secondary”: the clock synchronizes with the 

primary source. If the primary source becomes unavailable, it switches to the secondary source 
and stays there, even if the primary source becomes available again. It stays on secondary even 
if the secondary source becomes unavailable.

•

PRI – SEC – PRI or “Primary – Secondary – Primary”: the clock synchronizes with the primary 

source. If the primary source becomes unavailable, it switches to the secondary source. When 
the primary source becomes available again, it switches back to the primary. 

•

PRI – NSEC – PRI or “Primary – No Secondary – Primary”: the clock synchronizes with the 

primary source. If the primary source becomes unavailable, it switches to the secondary source. 
If the secondary source becomes unavailable, AND the primary is available, switches back to the 
primary.

Clock source switching is affected by the setting in F73 Timeout. When a reference source becomes 
unavailable, or unlocked, the number of seconds set in F73 Timeout must elapse before the switch 
occurs. While the reference source is unavailable the clock relies on a frequency source, such as its own 
oscillator or Aux Ref, to keep time. (If Aux Ref is available and enabled, the XLi will use Aux Ref as its 
frequency source. See 

 for more information.) 

After the timeout has elapsed, the switching sequence begins.

When a time reference becomes unavailable, the XLi switches to the other time reference, if available. 
The configuration of the time reference (e.g., Primary or Secondary) and the settings in 

 determine if and how switching takes place. If no other time reference is 

available, the XLi will use an Aux Ref frequency input on J3 (

) as its reference. If references are available, the XLi “freewheels” on its internal oscillator.