Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 187 of 265
2
2
4
4
S
S
T
T
A
A
G
G
E
E
M
M
O
O
V
V
E
E
M
M
E
E
N
N
T
T
R
R
E
E
S
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T
T
R
R
I
I
C
C
T
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I
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S
S
When a specific stage change is required not to occur for safety or traffic control
reasons, it is possible to restrict the move.
The types of restrictions available are:
(a) PROHIBITED MOVE:
This is the most restrictive and the effect is for the controller to stay on
the same stage and not look for other moves until the stage change
conditions are altered.
(b) ALTERNATIVE MOVE:
With this, the restricted move is not made but an alternative stage is
specified and a move to that stage takes place.
(c) IGNORED MOVE:
This is less restrictive than a Prohibited Move in that the restricted
move is ignored, but the controller looks for another satisfactory stage
change.
The above movement restrictions can apply in one or more modes, as specified on
the configuration sheets. Four sets of tables are available and each mode is
allocated to one of these tables, or to no table, if there are no restrictions for that
mode.
WARNING
To avoid the possibility of locking-up the controller, PROHIBITED
MOVES should not be applied during modes other than Manual, UTC
or CLF - IGNORE or ALTERNATIVE MOVES should be used instead.
If smooth plan changes are required in UTC and CLF Modes, (e.g. Hong Kong
Controllers), Prohibited and Ignore moves should not be used. See Sections 15 and
21.