Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 10 Page 86 of 265
6.2.6 Switched Sign Aspect
A switched sign aspect is an aspect of a hardware phase that is not allocated to a
stage but is illuminated and extinguished at certain times of day or when specific
conditions occur.
The normal functions of a switched sign aspect are as follows:
6.2.6.1 Secret Regulatory Signs
Secret regulatory signs, e.g. “No Right Turn”, “No Left Turn”, etc. are illuminated
and extinguished at a certain time of day when a specified associated phase loses
ROW.
6.2.6.2 WAIT Indicator for 3-Aspect Phases (Non UK Only)
When a pedestrian phase has a WAIT indicator the power to it is normally supplied
by the amber drive. If a pedestrian phase has 3-aspects (i.e. Red Man-Amber Man-
Green Man), or if a traffic phase requires a WAIT indicator, this drive is not
available.
A switched sign phase is then used. It is illuminated when the phase is not active
and a demand for it is present. It is extinguished when the pedestrian phase gains
ROW.
6.3 Conflicting Phases
Real phases that cannot appear at right of way together for safety reasons are
considered to be conflicting and as such must have inter-green times between them.
Phases which conflict but may never make a phase to phase transition due to stage
movement restrictions must also have inter-green times between them. This is to
cover the possibility of inter-green and minimum green times of phases in
intermediate stages being set low enough on the handset to allow the phase to
phase transition to take place. If the Customer does not specify an inter-green time,
it will be set to 5 seconds.
Phases that do not conflict, even if they never appear together in the same stage,
are considered to be non-conflicting phases and as such will not have an inter-
green time.
6.4 Opposing Phases
Demands for opposing phases are used to start phase maximum green timers.
Normally, phases that ‘conflict’ also ‘oppose’ each other. Dummy phases that would
conflict if they were real phases also oppose.
Phases that do not conflict but do not always appear together may be programmed
to oppose each other in order to start one or the others maximum green timers.