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Call Queue

The user needs to manage several calls.

The sample shows an example implementation of the call queue. It shows how further call handling functions can be integrated into the design by placing a hold button next to the end call button. The open non-modal dialog shows what happens when the operator tries to start another call during an ongoing conversation: The system displays the next reasonable options, like starting a conference.


The user needs to answer calls one by one, put active calls on
hold, and perform other management tasks.


Users may inadvertently double-press a call when trying to accept, which may result in trying to accept two calls subsequently. Furthermore, designing the case the queue overflows with too many waiting and held calls poses a challenge as well.


The solution proposes a call queue design consisting of 9 stacked slots at the right hand margin of the screen. These slots make up the call queue. The uppermost three slots are reserved for held calls, the 6 below are reserved for waiting calls. The example shows four waiting calls at the bottom of the queue and one held call in the third slot from above. Below, a big button is used to show the currently active call or the next waiting call in line in a ringing state. It is tightly coupled with the functionality of a handset: Picking up the handset connects the next waiting call as well. Arbitrary calls from the queue can be connected by pressing their corresponding call button. This slot is emptied, and all other calls waiting behind move down one slot. In this situation, the touch screen might record an inadvertent double click, so a key debounce must be inserted after pressing any button in the queue. There are a number of other call handling tasks that can be applied to an active call, for instance, putting a call on hold. The example screen shows the hold button next to the end call button; pressing it puts the currently active call in the next slot available for held calls — in this case, the second slot from above.

Usability Impact

Efficiency; error prevention

Safety Impact

This call queue prevents users to inadvertently end calls by separating the active call button and the end button, and by using a debounce on the call queue buttons.

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