Siemens EH.75M.11. Spezifikationen PDF herunterladen (Seite 116)

T400 Controller Facilities Manual

667/EB/20200/000 Page 9-56 Issue 9

9.11 FIXED TIME WORKING

There are two methods of obtaining fixed time working:

- Fixed Time mode

- Vehicle Actuated (VA) mode with permanent demands and extensions.

9.11.1 Fixed Time Mode

Fixed Time Mode is implemented:

- when FIXED TIME is selected on the mode select buttons subject to mode priority.

- by default, if there is no higher priority mode is active and no VA.

During Fixed Time mode, the controller cycles round a pre-programmed sequence of

stages disregarding local demands and extensions. The stage durations are exclusive to

the Fixed Time mode and do not include intergreen timings or phase delays which will

be implemented as during Vehicle Actuated mode. The stage duration can be changed

via the handset but the stage sequence cannot. Not all stages need be included in the

sequence. No stage can appear more than once in a cycle. If, for example a movement

is required to appear twice in the same cycle then two identical stages must be used.

Phases which appear conditionally will always appear in their corresponding stages, i.e.

there will be permanent requests.

The range of the timing period for the stage duration is 0 to 255 seconds in 1 second

steps. There is only one set of timings.

The programmed values may be changed via the handset using the FIX command.

Any all-red extension periods are automatically extended up to the maximum value to

ensure safe operation.

When Selected Fixed Time mode ceases, demands may be automatically inserted for

selected non-running phases to force a particular sequence. These demands are

normally inserted to ensure no vehicles are trapped against a red light, unless otherwise

requested by a customer.

9.11.2 Fixed Time to Current Maximums (VA Mode with Permanent Demands and

Extensions)

This method of fixed time operation can only be implemented with the use of special

conditioning.

When FIXED TIME is selected on the mode select buttons. The function of the button

is changed, using Special Conditioning, to select Vehicle Actuated mode and to insert

permanent demands and extensions for all phases, providing no higher priority mode is

active. The controller will then operate to VA mode strategy and not to a pre-

programmed sequence as in Fixed Time mode.

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Siemens EH.75M.11. Spezifikationen Seite 116