Siemens ST750 - Pedestrian Demand Cancel (Pdx); Kerbside Detector (Mat) Testing

ST750 GENERAL HANDBOOK
667/HB/33750/000 Page 41 Issue 6
• In VA mode, if no real phases in the same stream are at right of way, the delay is
introduced, so delaying the appearance of the pedestrian green after a quiescent
all-red period, for example.
• In all other modes, the delay will always be introduced. This is to cater for cases
such as ‘fixed vehicle period’ mode, UTC inserting a demand dependant force for
the pedestrian phase, or CLF introducing a demand dependant move just after
the push-button is pressed. Introducing the delay prevents these cases making a
stage move shortly after the push-button is pressed. In most other cases, the
demand delay will have little or no effect.
Note that special conditioning can always be written to ‘short-circuit’ the pedestrian
demand delay if required under certain circumstances by putting in an unlatched
demand for the phase if the wait indicator is lit.
3.3.4 Pedestrian Demand Cancel (PDX)
The unlatched phase demand is cleared when all kerbside detectors and their
extensions for the phase have been inactive for the configured pedestrian demand
extension time for the phase (PDX). The wait / demand accepted indicator will be
extinguished if there are no other demands present for the phase.
Note that the phase may still appear at green if the controller has already started the
move to the stage in which the phase appears.
3.3.5 Kerbside Detector (Mat) Testing
Kerbside detector testing can be performed by the firmware to check the operation
of kerbside ‘mat’ detectors.
Every 60 seconds, if there are no pedestrian phase demands active and no push-
button (or cycle) inputs active, the controller outputs a 500ms (±50ms) test pulse on
a configured output. If the output is de-allocated using IOA, no kerbside testing will
be performed.
This output is connected to all the kerbside detectors and should result in all of the
kerbside inputs going active during the pulse.
Therefore, the test is not performed while a pedestrian demand exists since this will
extend the pedestrian demand if the kerbside input has just gone inactive and the
controller is timing off the kerbside and demand extension periods.
Nor is the test performed while any push-button or cycle inputs (or their extensions)
are active since the kerbside test will activate the kerbside inputs even though no-
one may be present and allow these inputs to produce a demand for the pedestrian
phase.
Each configured kerbside detector is sampled twice and if either sample on a
particular kerbside detector indicates the detector is inactive*, the detector is logged