PT 5780 DVB-T Modulator
ProTelevision Technologies
Operating Instructions
Instruction Manual
Revision 3.11
4-31
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****** DEFAULT DATA LOADED ******
=- Release Keys -=
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On releasing the keys, the following window is displayed for approximately 1 second (LUI –
Local User Interface):
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********* REBOOTING *********
LUI Factory Reset
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After this the system reboots and the display reflects this. All system settings, as mentioned
earlier, return to their default values (shown as
bold
parameters in the menu system chart in
Chapter 4.3.2).
In an SFN system, the following variables are re-configured on carrying out a Factory Reset:
•
The SFN local delay is reset to 0
•
The SFN maximum delay is reset to 990 msecs
•
The SFN optional time, frequency and power offsets are reset to 0
Note as a result of the SFN optional time offset being stored in non-volatile memory, if the
instrument is moved from a location (stream) where optional data information was used to one
where optional data information is not used, it is necessary to carry out a Factory Reset to reset
this optional time offset parameter to 0.
4.5
SFN Mode of Operation
Special attention should be drawn to the following points regarding an SFN system.
SFN Mode and External 10 MHz Reference (Preferred mode of operation)
If the SFN system is set up with the 10 MHz reference source set to “External” and the external
reference signal is lost, the Reference Loss alarm will occur and the output signal is muted.
Using this reference setting in SFN will provide a system that mutes the output in case of loss of
frequency reference.
SFN Mode and Internal 10 MHz Reference
As the internal 10 MHz reference signal is asynchronous to the network, it should not be used
as a reference when operating an SFN system.
If the SFN system is set up with an internal 10 MHz reference signal, there will be no monitoring
of the external reference signals (and therefore no alarm) as they will not be used in the system.
Operating in SFN mode will normally always require that the modulator is locked to a network-
wide, common frequency reference. Seen in that perspective it is not recommended that the
INTERNAL REFERENCE setting and the SFN mode are combined, although it is technically
possible.
SFN Mode and Auto 10 MHz Reference
When the SFN system is set up with the 10 MHz source on auto-switching (“Auto”) and the
external signal is lost, the 10 MHz reference switches to the internal source and there is an
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