Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 10 Page 84 of 265
Note: it is a requirement in the U.K. that if audible and/or tactile indications are
fitted, the controller must also include the Red Lamp Monitoring facility, see section
38.2.
6.2.2.2 High Voltage Audible Indication (Not UK)
The audible signals are driven direct from the aspect supply to the pedestrian red
and green signals via relay contacts.
An I/O port can be used to drive a relay to disconnect the red and green feeds to the
audible signal when it is not required. Eight pedestrian signals can be controlled
usually by time switch control.
Eight relays are provided and driven from an output port bit to switch the above
feeds on and off.
The handset command “DET” for the specific output port/bit can be used to switch
this facility permanently ON, OFF, or allow it to follow the output state as dictated by
the controller logic.
6.2.3 LRT Phase
This is a phase used to control Light Rail Transit vehicles via a 2-aspect signal stop
and proceed. The ‘proceed’ may be ahead, left turn or right turn arrow, as required
by the method of control.
(N.B. If two different movements are required for proceed, e.g. ahead or left turn,
two phases must be used.)
The standard signal sequence is as follows:
at no ROW
- stop
at ROW (treated as a green for conflict purposes)
- proceed
leaving right of way (changing to No right of way)
- flashing proceed
6.2.4 Green Arrow Phase
A green arrow phase controls vehicle movements via a single aspect green arrow.
There are two types of green arrow – a ‘Filter Arrow’ and an ‘Indicative Arrow’:
6.2.4.1 Filter Green Arrow
A filter green arrow may be used to allow filter traffic to gain ROW in advance of the
main movement. It is illuminated during the stage or stages preceding the stage in
which its associated phase appears.
It will remain illuminated during the interstage period, normally until its associated
phase gains ROW, when it will be extinguished.