Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 196 of 265
times that do not required to be changed in an alternative plan should be set to the
same value as in the previous plan.
Any timer that is already active at the time of switching will remain effective until the
next start of that timing period. For example, if a maximum green of 50 seconds has
already started and the maximum is switched in the middle of that 50 seconds to a
new value of 30 seconds, the 50 seconds will still be timed. The 30 seconds will
become effective when that maximum green timer next has a reason to start.
Note: If a maximum green timeset is introduced using command/function code ‘3’ in
the timetable, the time switch event for the previously active maximum set is
automatically cleared.
26.3.3 Switch a Sign On/Off
Timetable settings may illuminate or extinguish a secret sign.
Note that two time switch functions exist, one to switch the sign on and one to switch
the sign off. However, the two functions should not
be used with the same sign. Only
one function should be used on a sign and which one depends on whether the sign
is to be switched on or off should the clock in the controller be incorrect, e.g. after
the power has been switched off for too long, see section 26.4
Note: The illuminating and extinguishing of a secret sign would normally be
dependent on the leaving amber of the associated phase as well as the timetable
setting. If this is required, Special Conditioning must be written to tie the secret sign
to the amber leaving of the appropriate phase as well as the timetable setting.
“SIGN ON” and “SIGN OFF” in timetable should not be used. Instead a conditioning
flag is used in timetable, see 26.3.6.
These time switch functions have been retained to allow easier upgrade of existing
configurations. Their use on new configurations is not recommended. Instead, use
Special Conditioning to control a Switch Sign and use the timetable function to set a
conditioning flag (26.3.6).
26.3.4 Switch a Stage/Phase In/Out of Cycle
Any stage, apart from the Start up and Part-time Shutdown Stages may be deleted
and re-introduced by a timetable setting.
If a stage is deleted, it will be omitted from the cycle until it is re-introduced.
If an optional real phase is deleted, the signals will remain at red (or blackout in the
case of a green arrow phase) whenever a stage that the phase normally appears in
is active. Note that fixed phases should not be deleted.
If a dummy phase is deleted, any effect its appearance has on stage changes or
timings will be cancelled.