Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 159 of 265
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17.1 Introduction
A ‘hurry call’ demand gives precedence to a particular stage to ensure that a green
signal is given to certain vehicles.
Hurry calls may be used at junctions, e.g. near to fire or ambulance stations, to
ensure that certain vehicles are given right of way, or in conjunction with queue
detectors, to prevent blocking of a junction.
Immediately a valid hurry call is received, the HURRY ACTIVE indicator on the
Manual Panel illuminates and remains illuminated until the end of the hold period. A
hurry call is valid provided its prevent timer is not active due to a previous hurry call
and the delay timer for any higher priority hurry call is not active. A cancel input for
each hurry call enables the process to be terminated any time during the delay, hold
or prevent periods.
17.2 Detailed Operation
There are eight hurry call units available on the controller (numbered 0 to 7) and the
facilities described below exist for each individual hurry call unit.
The programmed values may be changed via the handset using the commands in
brackets.
The hurry call for a stage is normally generated from a remote push button or
special detectors, but other calling conditions can be used if required.
On receipt of a hurry call request, the controller will go into Hurry Call Mode after a
pre-set delay, the hurry call delay period (DHC)
, providing the request should not be
rejected, see below:
The reasons for a request being rejected may be:
i) The controller is in a higher priority mode,
ii) The prevent timer being active,
iii) The delay timer for a higher priority hurry call being active (see section 17.5),
iv) The prevent timer on another hurry call unit is active (see section 17.5).
v) Hurry Call mode being disabled (see section 17.3 for some examples).
On expiry of the hurry call delay period, the controller moves immediately to the
requested stage, subject to stage movement restrictions, provided the inter-green
timings and minimum green timings associated with phases in the currently running
stage have expired. Extensions for running phases are ignored.
If the requested move to the hurry call stage is not permitted directly, the controller
can be programmed to move via the all red stage or other specified permitted stage
movements to the hurry call stage. If the move is accomplished via one or more
alternative stages, these stages terminate when their phase minimum green timings