Specifications
ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 223 of 265
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31.1 Introduction
There are often special requirements for the operation of a controller, which are not
covered by its normal methods of working. This is normally due to the peculiarities
of a particular intersection. For example it may be a requirement that demands for a
particular phase are inhibited during the first six seconds of appearance of another
phase, or a demand for a particular phase is inserted when there is a demand on
another phase and an extension on another, etc. Special Conditioning can cater for
this type of facility.
The operation required by Special Conditioning is specified at configuration and the
data is located in the configuration. This data forms a special software language that
is interpreted by the controller. The types of functions that can be performed are
described below.
For more information, see the IC4 Configurator Handbook.
31.2 Special Conditioning Operators
A large selection of controller variables can be read from Special Conditioning, and
a smaller selection of variables can be written to which will then modify the
operation of the controller.
A number of logical operations can be performed on variables that have been read.
These include the logical operations of ‘NOT’, ‘AND’, ‘OR’ and ‘EXCLUSIVE OR’.
The values of certain variables can be tested to see if they are ‘EQUAL’ to a
specified value or ‘GREATER’ than a specified value.
There are Special Conditioning timers that can be run and tested from within Special
Conditioning, started with time periods that can be altered using the handset.
31.3 Special Conditioning Examples
The following list is included to indicate the type and range of facilities that can be
provided by Special Conditioning:
Stages appearing more than once per cycle if many stages
Inter-greens extended by curtailed extensions
LRT prevent moves
Ped audible switched off/quiet by time of day
Dimming by time of day
Linking to remote pedestrian controllers or other controllers
Fault recognition of pedestrian controllers
Limit Green timer
Hurry call watchdog
CLF plans affecting VA operation