Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 137 of 265
15.3.1 Forces (F1, F2 etc.)
An ‘F’ control bit forces the controller to make an immediate move to the specified
stage, subject to any minimum green or inter-green periods timing off and any stage
movement restrictions.
An ‘F’ bit may be demand dependent if required. If it is, the move will only occur if
there is a demand for a phase within the specified stage.
If an ‘F’ bit remains active for longer than a configurable period (UWD), a fault
(FLF60) is logged and UTC mode will be disabled until the bit goes inactive. This is
to prevent the controller being held in one stage indefinitely
15.3.2 Stage Confirm (G1, G2 etc)
A single ‘G’ reply bit is returned when the specified stage is active, i.e. all fixed
phases within the stage are at green (see section 5.3).
If required, the controller can be programmed so that more than one stage returns
the same ‘G’ bit whenever the different stages are active. In this case the ‘G’ bit will
not stay active during any interstage between two stages with the same ‘G’ bit
unless the controller is specifically programmed to do so.
All the ‘G’ bits can be forced inactive, except the first two ‘G’ bits (normally ‘G1’ and
‘G2’) which are forced active, to indicate any of the following conditions:
a) Manual mode operating.
b) Manual mode selected.
c) No lamp power.
d) ‘Normal’ mode select button not selected, i.e. Manual, FT or VA selected.
e) ‘RR’ button pressed on the Manual Panel (if configured).
The G1/G2 reply bits are set independently for each stream, so that one stream can
set G1/G2 while another continues to return the correct ‘G’ bits. G1/G2 are assumed
to be the first two ‘G’ reply bits used on the stream. Therefore, if ‘G’ bits are
assigned to stages 1, 3 and 4, but not to stages 0 and 2, the ‘G’ bits for stages 1 and
3 would both be set if the signals are off.
The condition ‘no lamp power’ is also true if the Red Lamp Monitor (see section
38.2.3.2) or Part-Time Mode (see section 14.3) has extinguished the stream, while
the condition ‘manual operating’ is true only if the stream is actually running manual
mode (see section 18.3).
When ‘G1/G2’ is received at the central office the computer releases control
immediately. When ‘G1/G2’ stops being sent the computer will not normally regain
control until reset by the operator.
Normally ‘G1/G2’ is used to indicate no lamp power, i.e. condition (c). If it is used to
indicate any other conditions, the modes that are selected may not be a higher