Interaction Situation
The operation state of the robot needs to be transparent to the user at any time of the interaction. In all situations during which the robot is disconnected from the power network, the robot communicates that it is turned off and thus not able to generate any output and process any user input.
Solution
Let the robot express that:
To indicate the current operation mode of the robot it is recommended to use a dedicated status light that can be used independently of any other communication modality. This status light should be in an unobtrusive, non-attention grabbing color such as white, light yellow or light blue.
To show that the robot is turned off, the status light should be turned off.
Make sure to design a consistent behavior of the status light for the patterns Operation mode on, Operation mode off and Operation mode standby.
Related patterns:
Dependent on: Operation mode standby, Operation mode on
Opposed Patterns: Operation mode standby, Operation mode on
Examples
Rationale
In human-technology interaction it is very common to indicate the operation mode of a device through a glowing light. The light is not glowing if the device is turned off, which makes it easy for the user to understand the operation mode of the device in an instance.