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The operator wants to join several participants in one conference call.


Especially in en-route centers conference calls are common, whereas in signalling centers they are less frequently used.


The standard PABX conference procedure is hard to recall, especially for infrequent users. The display of an active conference also needs to provide ways to remove participants from a conference and to monitor their connection status.


Provide two versions of the conference function: 1. the standard procedure, which experienced, heavy-duty phone users are familiar with, and 2. an improved version for less frequent users. The description of the procedures below assumes an active call to begin with.

1. Standard procedure. The operator then presses the conference key and makes a call to the first participant to join the conference. After the party responds and the operator presses the conference key again, all three are joined in a conference call.

2. The improved procedure allows the operator to select participants from whichever source, for instance, the speed dials, the phone book, and others. The conference starts automatically once the operator makes another call during an active call. The system asks the operator what to do with the selected participant, to hold, join in a conference, or to replace the currently active call.

Usability Impact

Efficiency, user satisfaction, learnability

Safety Impact

A conference can be quickly established, which is of use especially in a dense situation. The intuitive procedure makes conferencing easy to recall.


Has been used in several European railways voice communication devices.

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