Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 10 Page 88 of 265
A stage change will not take place until the minimum green times for all phases that
need to terminate have timed off.
The timing range is 0 to 255 seconds in 1-second steps. There is one minimum
green time and one set of range limits for each phase.
6.5.2 Green Extension (EXT or IPX)
When a ‘vehicle actuated’ phase (i.e. a traffic, green arrow or dummy phase) is at
green, it is possible to extend it past the minimum green period by means of green
extensions, up to a maximum green period.
The occupation of an extension loop will generate a green extension for its
associated phase. The green extension will continue while the loop is occupied.
When the extension loop is cleared, the green extension will continue for a fixed
period - the extension time. The timer will be restarted if the loop is occupied again
before the extension time expires.
The phase cannot be terminated whilst the green extension is active unless it is
legitimately overridden (e.g. maximum green timer terminating or under influence of
UTC or CLF).
It is also possible to program the controller so that extensions for a phase are lifted
during any stage that the phase appears in.
If no vehicles are detected for a period longer than the extension time, the extension
timer will terminate and the phase will ‘gap change’ if there is an opposing demand.
The timing range is 0 to 31.8 seconds in 0.2-second steps. There is one extension
time for each phase or optionally, one for each detector.
Each phase can be configured with a number of extension detector inputs.
If the extension time is configured against the phase (using the EXT handset
command), the extension time commences when all of these detector inputs have
gone inactive.
If the extension time is configured against the individual detector inputs (using the
IPX handset command), each detector has its own extension timer that commences
when the input goes inactive. The green extension on the phase will cease when all
of its detector inputs and extensions are inactive.
If extension times are configured against the individual detector inputs (using the
IPX handset command), phase extension time (using the EXT handset command)
should be set to zero.