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Dial Pad

The user needs to enter a structured number consisting of multiple parts of different format.


Enter a number using the digit block and select options for making your call.


The operator needs to call a participant neither knowing the telephone number nor having a shortcut like a speed dial nor a phone book entry.


The operator should not be forced to look up numeric codes when composing the number. The procedure must be efficient and reduced to a minimum number of steps.


The proposed dial pad assists operators in composing numbers by encapsulating numeric codes in meaningful entities for easy selection. Numbers may consist of several parts, for instance, the example uses a three-part number structure. The first part is the call type, which is visualised as a selector control with “Train” selected. The second part is the number, which must be entered using a digit block. The last part is a numeric code corresponding who on the train shall be called.

Usability Impact

Error prevention, cognitive load, user satisfaction

Safety Impact

Relieving the operator of the need to look up codes in long tables reduces cognitive load, and therefore, the error probability. Trains usually must be called quickly, therefore, any acceleration in entering a number can be considered a safety improvement.

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