DOC 6501_Release V
ATS-6501 Users Guide
193
Appendix E System Recovery Without GNSS
This procedure provides the steps, commands, and information needed to recover the ATS-6501
without a GNSS reference input. It is assumed users have enough knowledge about their
configurations to determine the best methods to recover UTC and the potential risks and errors
associated with these steps. If there are two ATS 6501s used in a system as redundant sources for
ATS 6511s, the ATS 6501 supplying fiber signals to the B inputs should be left in a state with no
outputs until the A input ATS 6501 and all ATS 6511s are fully set up.
It is possible to recover UTC using another 6501 in holdover with either an internal or external
Time Interval Counter or using an ATS-6502 Time Transfer Modem.
1. Ensure the ATS-6501 is powered up and telnet into the command port (1700).
2. Change the system settings to allow the time recovery:
a. Change reference from external to internal. reference internal
b. Change the steer_source from GPS to manual. steer_source manual
3. Recover the system time.
a. ATS-6502: If the local unit is still tracking the remote unit and is set up to use NTP over
the link it can set the system time from the remote unit. Use the force _time <ntp server
ip> to point to the 6502 to set the ATS-6501 system time.
b. Date-Time: Use the force_time YYYY-MM-DD-HH:MM:SS to set the date time as
close as possible to the current time.
c. NTP Server: If the system can communicate with a NTP Server user the force_time <ntp
server ip> command to obtain the current time from an NTP Server. To verify the system
time is correct use the remote_ntp_offset <ntp server ip> command to verify the system
time is within 1 Second of the remote NTP Server.
Note: This step will turn the outputs on. All of the downstream 6511s will now have at least one
fiber input as a reference.
4. If needed, use the adjust_time command to move the second on the ATS-6501 in interval
seconds up to +/- 1000 seconds. The step above should have the time very close and only
minor adjustments should be needed to align the ATS-6501 onto the correct second.
Note: If could take up to 45 seconds for all of the downstream ATS-6511s to set their clocks to
the correct second after this adjustment is made.
5. Once the system is close to the correct second use the adjust_pps command to adjust the
fractional second so the 1PPS output is within 100 nSec of the external reference. The
adjust_pps command will adjust the PPS output from +/- .5 Seconds.
6. Use the jam_sync command on the ATS-6511 driving the ATS-6502.
Note: It is possible the ATS-6511s may report the fiber from the ATS-6501 being recovered as
“dark” after the adjust_pps commands are executed. It is recommended you perform a restart --
cold on the ATS-6511 driving the ATS-6502 to clear this condition. Once this unit restarts and
turns the outputs on, use the recal command on the ATS-6502 to recalibrate the system to ensure
the reported measurements are accurate.
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