Meinberg LANTIME, Operating Instructions Manual

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If it is necessary to provide redundancy against hardware failure then it is also
possible to install several LANTIME NTP servers in the same network.
LANTIME/SHS: Modes Of Operation
Normal mode of operation: Both the radio clocks are synchronized to their primary
time sources, the difference between the independent reference times is below the
configured limit. The NTP server receives the time information including the status
"synchronized", so it acts as Stratum-1 server and makes the reference time available
to the network.
One of the radio clocks falls out of sync e.g. due to an antenna failure or other
reception problems. The clock changes its status to "not synchronized" and continues
counting time based on its built-in high-accuracy crystal oscillator. Depending on the
configuation, it takes some days up to several weeks until the difference between the
time signals exceeds the limit. Since one of the radio clocks is still synchronized, the
timing information is passed to the NTP server with status "synchronized" until the
limit is exceeded.
Both the radio clocks are not synchronized to their primary time sources although
at least one of them has been synchronized before . As long as the time difference
doesn't exceed the limit, the time information is passed to the NTP server, but the
status included is set to "not synchronized". The NTP server keeps accepting the time
information for a given trust time, after the trust time it discards the time information.
Both the radio clocks are not synchronized to their primary time sources and have
not been synchronized after the last power-up . The hybrid clock does not pass any
time information to the NTP server until at least one of the independent radio clocks
is synchronized and the time difference between the clocks is below the configured
limit.
The radio clocks output time information with a difference which exceeds the
configured limit , or one of the radio clocks does not output any time information
at all . One of the following circumstances can be the reason why:
An intended external fake
Failure or malfunction of one of the primary time transmitters
Failure or malfunction of one of the radio clocks
Persistent reception problems
In all the cases listed above the plausibility checks on the timing information fail ,
so the hybrid radio clock stops passing any timing information on to the NTP server.
The NTP server's stratum changes to a worse value to let the clients know that the
server's reference time source fails. The hybrid radio clock continues supplying time
to the NTP server after all error conditions have been removed and the
error has
been acknowledged by an operator.
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