Nevion 3GHD-CHO-2x4 - Manual (Page 14)

3GHD-CHO-2x4/2x3 Rev. C
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8.6 Change over block
The change over block is cal led “main input” and all alarms from the change over block are
labeled “main input”. *In the following figure the change over function is explained.
The main input is selected. The other input will automatically be the backup input.
In the rules radio button loss of lock or loss of input signal is chosen for the main trigger for
doing change over. Addition to this rules and EDH trigger can be setup, see chapter 8.7.
The trigger has an adjustable time control, called "hold time" and “lock time”. This is used for
three situations:
1. Multiple bursts of error within timer duration triggers a switching to standby.
2. Single continuous error condition whose duration exceeds timer triggers a switching
to standby.
3. Error free periods, whose duration exceeds timer, triggers a switching back to main.
The “hold time” is for main to backup trigging while the “lock time” is for backup to main
restoring of the signal.
The latch will select the behavior of the change over. The following block diagram explains the
behavior of the change over.