Device Sensors Understanding

Understanding Device Sensors

Intent

The intent of this success criterion is to ensure that functions that are triggered by device or user motion can also be operated by user interface components, unless the motion is essential for the function and not using it would invalidate the activity.

Note: This criterion concerns input through sensors which respond directly to motions such as tilting, shaking, or panning. It is not intended to cover indirect motion associated with operating a keyboard, pointer, or assistive technology.

Devices may have sensors that act as inputs, e.g., tilt/orientation or motion sensors on a phone or tablet device, allowing the user to control something by simply changing the orientation or motion of the device in space. Some users with disabilities may not be able to operate these sensors (either not at all or not precisely enough) because the device is affixed to a wheelchair or due to motor impairments. Functionality must therefore be implemented in a way that other means are available to activate the function that do not rely on sensor input.

Some applications are specifically created to use device sensor data. Examples of content that are exempt from this requirement include a pedometer that relies on device motion to count steps.

Benefits

• This Success Criterion helps people who may be unable to perform particular actions (such as tilting or shaking) because the device may be mounted or users may be physically unable to perform the necessary action. This success criterion ensures that users can still operate all functionality by other means (e.g., touch or voice input).
• All users may benefit, for example, users who are temporarily unable to hold and move the device because their hands are occupied with some other activity.

Examples

• After text input in a field, shaking a device shows a dialog offering users to undo the input. A cancel button next to the text field offers the same functionality - activating it reverts to the content (if any) that was shown before the user input replaced it.
• A user can tilt a device to advance to the next or a previous page. Buttons or links are also provided to perform the same function.
• A user can move or pan a device to change the view in an interactive photo. A control is also available to perform the same function.
• A user can turn a device to change map orientation. A control is also available to perform the same function.

If the scope of device sensors covered by this SC is to include sensors other than just motion sensors, the following examples might also apply:

• An application uses a camera to detect user hand gestures and interprets them to control a game character. A control is available to perform the same function.
• An application uses a sensor to monitor light level changes and adjusts the colors presented on the screen. A control is available to turn off the automatic adjustment.

Sufficient

• Functionality/content must not solely rely on device inputs (e.g. an alternative which does not require the user to manipulate their device/use these device inputs must be available)