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T400 Controller Facilities Manual

667/EB/20200/000 Page 9-6 Issue 9

9.3 URBAN TRAFFIC CONTROL (UTC) MODE

(Normally an O.T.U. is required for this facility.)

In UTC mode, operations are controlled and monitored by the central computer of an

Urban Traffic Control system.

Stage changes are effected by the application of forces and demands. The demands

may either be local or simulated by the computer. During UTC mode maximum green

timers normally have no effect and are held in a RESET state.

Instation equipment at the central computer office communicates via telephone lines to

an outstation transmission unit (OTU) housed within the controller. This method

conforms to Department of Transport Specification MCE 0312.

Control signals are transmitted as two 8-bit control words and monitoring signals are

returned as two 8-bit reply words. Figure 21.14 illustrates a bit format for the

intersection in section 21.

Interfacing of the control and reply signals between the OTU and the controller is via

reed relay buffers (see section 15).

The logic states of the control and reply bits at the controller are as follows:

ACTIVE INACTIVE

CONTROL: ‘CLOSED (1)’ ‘OPEN (0)’

REPLY: ‘OPEN (0)’ ‘CLOSED (1)’

Any unused reply bits are usually set to the inactive state.

9.3.1 Method of Plan Introduction

Certain contracts require that the controller must synchronise with the Plan quickly.

To achieve this, the following constraints are placed on the UTC facility:

The Stage movement restraints table used by UTC should not have purely

prohibited moves or Ignore moves configured. They should either be allowed

moves or if this is not acceptable for safety reasons, then alternative moves

should be specified. If alternatives are specified, it is preferable for the

alternative stage to be one or two stages ahead in cyclic order of the original

target stage, for example:

if the move 1-2 is not to be allowed,

the alternative could be 1-3 or 1-4.

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Siemens EH.75M.11. Especificaciones Pagina 66