Specifications
ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 128 of 265
Bus/LRT/Emergency Vehicle Priority mode: Entered if a request exists for
priority from a special vehicle detector, (e.g. LRT request).
Vehicle actuated or fixed time mode: Entered if a request does not exist for a
higher priority mode.
12.1 Mode Priority
The mode priority facility allows for the mode with the highest priority for which
operating conditions are active (e.g. force bits from the UTC computer or a hurry call
demand) to be the current mode. When the operating conditions become inactive,
the next highest priority mode with operating conditions active will become the
current mode. It need not necessarily be the next one in line. If at any time operating
conditions for a higher priority mode become active, that mode will become the
current mode. If more than one set of operating conditions is active, the mode with
the highest priority will become the current mode.
For priority purposes, SELECTED MANUAL CONTROL and SELECTED FIXED
TIME, CLF OR VA are considered as modes. The operating conditions for these
modes are the relevant mode select buttons being selected, i.e. MANUAL, FIXED
TIME, CLF or VA.
Fixed Time, CLF or VA modes selected via the Manual Panel are considered as
different modes to ‘normal’ VA, CLF or Fixed Time modes. This allows VA or fixed
time to be configured as the lowest mode, i.e. the one in which the controller will
operate if no higher priority modes are requested. Whilst SELECTED VA or FIXED
TIME mode can be configured higher up the mode priority table, so that if
necessary, the controller can be forced to operate in VA or Fixed time, even if there
are requests for modes of higher priority than the basic VA or Fixed time.
For example:
Priority Mode(s)
1 Manual
2 Selected VA, CLF or fixed time
3 Hurry
4 Priority
5 UTC
6 CLF
7 VA
This will allow the controller to be forced to operate in the selected mode even if any
of modes 3-6 are requested to be active.
To select Fixed Time, CLF or VA, the appropriate mode select button on the Manual
Panel must be selected.
Similarly to select Manual mode the MANUAL mode select button is selected and if
SELECTED MANUAL CONTROL is a higher priority than the current mode, manual
mode will become operational.