Specifications

ST900 Family General Handbook

667/HB/32900/000 Issue 11 Page 155 of 265

If the priority mode is configured lower priority than UTC mode, while force signals

from the UTC instation are being received and the controller is in UTC mode,

requests for the priority mode will be ignored.

However, if the priority mode is already active when force signals are received from

the UTC instation, the controller can be configured to operate in either of the

following ways:

a) (Default) The controller immediately enters UTC mode as normal, ignoring

the request for priority mode and terminating any of its actions.

b) However, if the ‘Introduction of UTC to be disable by Priority Mode’ (see the

general UTC screen in IC4), the priority change is allowed to complete before

the controller enters UTC mode.

16.4 Priority and Emergency Vehicle Parallel Stage Streaming Facilities

Each stream will move around its own stages according to its own Priority or

Emergency Vehicle demands and extensions independent of any other streams.

However, if two or more priority units are configured on phases within the same

stream they will interact, see section 16.3.

16.5 Visual Indications

A separate indicating light emitting source is normally provided, behind the Manual

Panel door of the controller. Whilst a priority vehicle is detected, the handset may

be used to determine which priority unit has been demanded.

For each priority stage equipped with an ‘inhibit period’, a display is available on the

handset to indicate that an ‘inhibit period’ is running.

For each priority stage equipped with a compensation period, a display is available

on the handset to indicate a compensation period is running.

Handset facilities are provided at the controller to enable:

(a) A permanent priority demand to be inserted.

(b) The priority facility to be permanently disabled.