5700MSC-IP
IP Network Grand Master Clock & Video Master Clock System
Page - 42 Revision 0.2
User - When the time comparator detects a difference between the system clock and the time
reference, it will notify the operator with a jam warning. The message “TIME JAM NEEDED” will be
displayed on the front panel, and optionally an SNMP trap can be sent. The operator can then decide if
and when to perform a jam in order to cause minimum disruption to systems. This mode should be
selected when the time outputs of the 5700MSC-IP require absolute minimum disruptions.
Daily - The time comparator is shut off in this mode. A jam will be performed once a day at the time
specified by the Input Jam Time control. This way the system clock can be brought into sync with the
reference regularly, at time of day when any disruptions would go unnoticed.
When the Time Reference is set to SNTP, the Time Lock Type is forced to Daily.
A manual time jam can be initiated using the Jam Time menu item. When a time jam
is performed, all timecode clocks are also jammed. Exercise caution before initiating
a jam.
3.3.2. Coordinated Universal Time (UTC)
Coordinated Universal Time (UTC) is used worldwide as the basis of civil time and runs at the same
rate as International Atomic Time (TAI). Unlike atomic time, Coordinated Universal Time is kept within
one second of mean solar time, or Greenwich Mean Time (GMT). The rotation of the earth is very
slightly slowing which causes the solar day to lengthen by a fraction of a second. This introduces a
slight error between atomic time and solar time. Over weeks, months, and years, the error can add up
until atomic time is a full second ahead of solar time. Because UTC runs at the same rate as atomic
time, it must be slowed down if it is to match solar time.
Leap seconds are introduced periodically and cause UTC clocks to count one extra second in a day to
slow them down. The rotation of the earth is unpredictable which means the need for a leap second
cannot be predicted more than six months in advance. If a leap second is necessary, it will occur at the
end of the day usually on either June 30
th
, or December 31
st
. Refer to www.iers.org for more
information and bulletins on upcoming leap seconds. Leap seconds can cause complications with
25Hz LTC or PAL VITC.
The 5700MSC-IP expects that the time reference provides UTC time. This is a requirement for the
NTP server hosting using the NRC protocol.
3.3.3. Time Reference Sources
The system clock can be referenced in one of several ways. The reference type is selected in the
Time menu located in the INPUT root menu. The Reference Src menu item is used to select between
GNSS, LTC, VITC, IRIG, SNTP, 1588 and None. Note that the time reference will be forced to GNSS if
the frequency reference has been set to GNSS, no matter what has been selected here.
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