3.7.3 Disable Holdover Limit
When checked, this option allows the holdover limit of the device to extend forever. The TM2000A
requires a GPS lock to initially set its time, but by checking this option, it can then be run without a
GPS lock. The time WILL drift off of standard at a rate that is dependent on the accuracy of the OCXO
of the device, but this option is included for cases where exact accuracy isn't required, just
synchronization of devices withing a closed system. Drift has been measured as high as 0.1 seconds
per week.
3.7.4 NTP Holdover Accuracy
This slide bar is used to set your required accuracy during holdover when 3D lock is lost. This will
range from 1ms @ 3 hrs to 10ms @ 30 hrs. The device will change to Stratum 16 when the set
holdover time is expired and 3D lock is not achieved. The accuracy of this setting is an average
determined from experimental testing of a number of TM2000A units compared to a reference clock
source while running without a GPS lock. Some units will perform better, some a bit worse.
3.7.5 PTP Transmission Method
The PTP transmission method can be set to either Multicast or Unicast. Select the desired mode of
operation and click the Submit button.
3.7.6 PTP Post-Holdover Behavior
There are two options here: Update Clock Class to 52 which in the PTP protocol means: “A clock of
clock Class 52 shall not be a slave to another clock in the domain.” If set to Faulty, it will report as
Faulty and should not be synced to by a client.
3.7.7 Multicast Configuration – Log Announce Interval
Set the announce message interval. The rate of sync packets is 2^(-value). The default setting of 1,
sets the interval at 2^(-1) = 0.5 packets per second, or every 2 seconds.
3.7.8 Multicast Configuration – Log Sync Interval
Sets the requested Sync Message Interval. The rate of sync packets is 2^(value). The default of -7,
therefore makes the default rate 2^-7 = 128 packets per second.
Installation and Operations Manual | Page 11
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