Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 156 of 265
16.6 Interfaces
16.6.1 Inputs
An input channel may be provided such that Condition ‘0’ will cause the bus priority
facilities to be isolated. Bus priority demands need not be stored. The input will take
effect irrespective of the state of computer control force bits.
16.6.2 Outputs
An output channel will be provided to indicate that stage confirmation signals may
not be as required by the computer/linking plan. Condition ‘0’ will be returned to
indicate that the controller is operating at a priority level (either bus or emergency
vehicle).
A separate output channel for each bus priority stage may be specified. Condition ‘0’
will be returned to indicate the presence of a bus demand or extension.
A separate output channel for each emergency vehicle priority phase may be
specified. Condition ‘0’ will be returned to indicate the operation of an emergency
vehicle detector. (This may be used to synchronise a “green wave”).
16.7 Use of Priority Mode for Control in Light Rail Transit Systems
Figure 29 is a block diagram of the additional features available in Priority mode that
may be used when controlling Light Rail Vehicles.
USED IN SPECIAL
CONDITIONING TO PREVENT
CERTAIN STAGES
USED IN SPECIAL CONDITIONING
TO EXTEND THE ALL RED IF AN
LRT PHASE TERMINATES WITH AN
LRT REQUEST STILL PRESENT
‘C’ ‘B’
ENABLE
‘A’
ASSOCIATED LRT REQUEST
SIGNAL PRIORITY UNIT 1
FIRST COME FIRST
SERVED LOGIC
DELAY PERIOD 1
DELAY FOR
DISTANCE BETWEEN
REQUEST
DETECTOR AND
JUNCTION
DELAY PERIOD 2
DELAY TO ALLOW
INSTANT SERVICE
ON PRIORITY CALL
LRT
REQUEST
SIGNAL
PRIORITY
UNIT 0
AND
SPECIAL
CONDITIONING
INPUT / OUTPUT
PRIORITY SECOND
DELAY TIME - ‘PSD’
ON THE HANDSET
(0-255 SECONDS)
PRIORITY FIRST
DELAY TIME - ‘PFD’
ON THE HANDSET
(0-255 SECONDS)
PRIORITY UNIT 0
PRIORITY INPUT
VA DEMAND
VA INPUT
AND
Figure 29 – Priority Demand Order