Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 10 Page 106 of 265
7.3.2 Pedestrian Push-Buttons
When a pedestrian push-button is pressed, a ‘latched demand’ is inserted for the
pedestrian phase that will give right of way to the pedestrian and the associated
WAIT indicator(s) are illuminated. See section 7.4 for more information.
If it is required, it is possible to illuminate the WAIT indicator without inserting a
demand or conversely insert a demand without illuminating the WAIT indicator.
Also see section 24.6 on ‘Cross Inhibit Linking’.
7.3.3 Pedestrian Kerb-Side Detectors
See section 7.4 for details on Pedestrian Kerbside Detectors.
7.3.4 Pedestrian On-Crossing Detectors
‘On-Crossing Detectors’ are above ground detectors that are used to determine
when pedestrians are still crossing. While pedestrians are still crossing, the
extendable clearance period is extended, up to its configured maximum (CMX).
See section 6.11 for more details on the different pedestrian phase types and their
clearance periods.
If an on-crossing detector has not been activated since the end of the previous
extendable clearance period (CMX) it is treated as suspect, forcing the current
extendable clearance period to run to its maximum. Monitoring of an on-crossing
detector continues during the current extendable clearance period, such that if the
detector is activated during this period, it is no longer treated as suspect.
A fault will not be recorded if this occurs, instead the controller will wait until the
normal DFM time-outs confirm and report a fault.
Also note that if the Continuous Ped Demand (CPD) button on the Manual Panel is
pressed, the red clearance of near-side signals will be extended to its maximum as
required by TR2500.
7.3.5 Revertive Demands
When a vehicle actuated phase terminates with an extension still active, e.g.
because the maximum green timer expired, a revertive latched demand is inserted
for the phase to prevent any vehicles being trapped between the detectors and stop
line without a demand for the phase.
If required, the revertive demand may be inserted for an alternative phase rather
than for the terminated phase.