Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 122 of 265
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11.1 General Description
In order to gain more efficient use of phases during stage to stage transitions, it may
be required to delay specific phases from losing or gaining ROW.
There are up to 120 phase delay times (0 to 119) available for different phases on
different stage to stage transitions.
The timing range is 0 to 255 seconds in 1-second steps.
Special conditioning can disable and enable individual phase delays and thus is
able to change the delay time (by time of day for example) by only enabling one of
several phase delays configured for the same phase on the same stage to stage
transition.
11.2 Phases Losing Right-Of-Way
A phase may be delayed from losing ROW on a specific stage to stage transition to
obtain a clearance period.
The delayed phase is held at green during the interstage for the period of the delay
time, while non-delayed phases that do not appear in the next stage terminate. Any
inter-green periods from the delayed phase to conflicting phases will not commence
to time until the phase delay period has expired, even though other inter-green
timers from phases already terminated will have started and possibly terminated.
Therefore any phases gaining right of way may have their appearance delayed as a
result of the difference in inter-green times, unless the inter-green times from the
delayed phase are shorter.
In Figure 26 (overleaf), the appearance of phases E and F is controlled by the 6-
second inter-greens from phase A. The shorter inter-greens from phase B mean that
phase B can remain at right of way for an extra second without affecting the
appearance of phases E and F.