Chapter 3: Common Functionality

  • 301  General
  • 302  Closed Functionality
  • 303  Biometrics
  • 304  Preservation of Information Provided for Accessibility
  • 305  Color
  • 306  Flashing
  • 307  Operable Parts

301 General

301.1 Scope.  The provisions of this chapter shall apply where required by Chapter 1 or where referenced by a requirement in this document.

302 Closed Functionality

302.1 General.  ICT that has closed functionality shall conform to 302.

Advisory 302.1 General.  ICT has closed functionality for many reasons.  These reasons include design or policy.  ICT may have closed functionality in practice even though the manufacturer did not design or develop ICT to be closed.  Computers which are “locked down” to the extent that end users cannot adjust settings are functionally closed.

Information kiosks and most hand held calculators have closed functionality because their functionality is self-contained.  By design, no provision is made to add peripherals to them.  Examples of peripherals include alternative input and output devices.

An example of ICT that has closed functionality is an electronic “book” that is “locked” by the publisher.  The “lock” prevents the content from being converted into alternate formats.

As a result of using Digital Rights Management (DRM) technology, publishers sometimes prevent visual content from being played in audio form (or audio content from being displayed in visual form).  A best practice is for publishers not to implement DRM technology which creates barriers to accessibility.  An alternative best practice for publishers is to provide an alternate format which is compatible with assistive technology.

Electronic content, including “e-books”, holds great promise for people who have limited cognitive ability, limited or no vision, or limited manipulation.  Electronic copy is much more flexible and adaptable than hard copy paper, and includes the ability to be read in alternate formats such as large print or braille.

302.2 Without Attachment of Assistive Technology.  ICT that has closed functionality shall be usable by people with disabilities without requiring assistive technology other than personal headsets for private listening, to be attached.

303 Biometrics

303.1 General.  When biometric forms of user identification or control are provided, ICT shall conform to 303.

Exception:  When the biometric form of user identification or control employs biological characteristics possessed by all people, conformance to 303 shall not be required.

Advisory 303.1 Biometrics General Exception.  Examples of biological characteristics that all people possess are DNA and circulatory systems.

303.2 Alternate Identification or Control.  ICT shall provide an alternate form of user identification or control that conforms to either 303.2.1 or 303.2.2.

Advisory 303.2 Alternate Identification or Control.  Biometrics use biological characteristics for user identification or control.  Examples of biometrics used for identification or control include but are not limited to:  fingerprints, retinal scans, iris patterns, voice prints, facial recognition, and hand veins.  However, people with disabilities might not possess all biological characteristics.

Biometrics that are restricted to a single biological characteristic pose a significant barrier to people with disabilities who do not possess that specific biological characteristic.

This provision requires ICT that uses biometrics either to provide for two (or more) dissimilar biological characteristics, or to offer an alternate mode for user identification or control.

303.2.1 Alternate Biometric.  An alternate biometric that uses a biological characteristic dissimilar to the biological characteristic of the default biometric shall be provided.

Advisory 303.2.1 Alternate Biometric.  Examples of biometrics that rely upon dissimilar biological characteristics are voice recognition and face recognition.  Biometric methods based on dissimilar biological characteristics increase the likelihood that people with disabilities possess at least one of the specified biological characteristics.  Examples of dissimilar biological characteristics are:  fingerprints, eye retinal patterns, voice, and face.

Examples of biometrics that rely upon similar biological characteristics are finger printing and thumb scans.

303.2.2 Non-Biometric Alternative.  A non-biometric alternative that does not require the user to possess any specific biological characteristics shall be provided.

Advisory 303.2.2 Non-Biometric Alternative.  An example of a non-biometric form of user identification or control is entering a pass code.

304 Preservation of Information Provided for Accessibility

304.1 General.  ICT that transmits or converts information or communication shall conform to 304.

304.2 Encoding, Compression, or Transformation.  ICT that transmits or converts information or communication, shall not remove non-proprietary information provided for accessibility or shall restore it upon delivery.

Advisory 304.2 Encoding, Compression, or Transformation.  This provision applies to ICT using industry-standard codes, translation protocols, or formats.  It applies to conversion techniques, such as encoding, signal compression, and format transformation.

Examples of ICT that encode, compress, or transform include firewalls, routers, and gateways.

An example of ICT preserving information provided for accessibility is a media player that displays embedded captions from a captioned video and does not strip out the captioning.

Another example of preserving information provided for accessibility is converting a document into a new format while retaining information about the identity, operation, and state of the interface elements.

This provision does not require the addition or translation of information.  For example, this is not a requirement to change voice mail to text or to vocalize captions.

305 Color

305.1 Not Only Color.  ICT shall not use color as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

Advisory 305.1 Not Only Color.  This requirement allows color to be used.  An example is an electronic form with required and optional fields.  Instructions at the beginning of the form explain that required fields are both labeled with an asterisk and appear in red text.  In this example, the asterisk is the non-color dependent visual means of conveying information.

This provision only addresses the ability to distinguish color.  Other forms of perception are addressed by 503.2 Information, Structure, and Relationships which includes programmatically determinable access to information conveyed by visual presentation.

306 Flashing

306.1 Flash Threshold.  When ICT emits lights in flashes, there shall be no more than three flashes in any one second period.

Exception:  Flashes that do not violate the general flash or red flash thresholds are not required to conform to 306. 

Advisory 306.1 Flash Threshold.  For further clarification of this requirement, consult WCAG 2.0 Success Criteria 2.3.1 “Three Flashes or Below Threshold”.

See also the WCAG 2.0 definition for “general flash and red flash thresholds” found at:

307 Operable Parts

307.1 General.  ICT with operable parts shall conform to 307.

307.2 Clear Floor Space.  A clear floor or ground space conforming to 36 CFR Part 1191 Appendix D, Section 305 shall be provided for ICT with operable parts.

307.3 Height.  ICT with operable parts shall be placed so that the operable parts are within one or more of the reach ranges conforming to 36 CFR Part 1191 Appendix D, Section 308.

Advisory 307.3 Height.  This provision applies to reach ranges applicable to both forward and side approaches.  Diagrams appear in ABAAG/ADAAG (36 CFR Part 1191).

307.4 Operation.  ICT with operable parts shall be operable with one hand and shall not require tight grasping, pinching, or twisting of the wrist.

307.4.1 Activating Force.  The force required to activate operable parts shall be 5 pounds (22.2 N) maximum.

307.5 Touch-Operated Controls.  ICT with controls that are designed to be operated by touch using the fingers, including but not limited to keys, buttons, switches, and touch pads, shall conform to 307.5.1 through 307.5.3.

307.5.1 Tactilely Discernible.  Controls shall be tactilely discernible without activating the controls.

307.5.2 Locking or Toggle Controls.  When ICT has locking or toggle controls, the status of all locking or toggle controls shall be visually discernible and discernible through touch or sound. 

Advisory 307.5.2 Locking or Toggle Controls.  Locking or toggle controls are those controls that can only have two or three values and that keep their value while being used.

An example of locking or toggle controls is the “Caps Lock” key found on most keyboards.  Another example is the volume button on a pay telephone which is set at normal, loud, or extra loud volume.  An example of making a control discernible is when a sound is emitted when a user runs a mouse over a control. 

307.5.3 Key Repeat.  When key repeat is supported by a keyboard interface, the delay before key repeat shall be adjustable to at least two seconds.

307.5.3.1 Adjustability.  Key repeat shall be adjustable to two seconds per character.

Advisory 307.5.3 Key Repeat.  Key repeat is the keyboard feature in which a typed character is repeated by holding down a single key.  Key repeat can pose a problem for accessibility.  If the repeating starts too soon, or if the repeat happens too quickly, slow typists can end up with lots of extra characters which are cumbersome to remove.  Use of the backspace delete key also relies upon delay before repeat and repeat rate being controllable.

307.6 Non-Mechanical Controls.  ICT that utilize non-mechanical controls shall provide an alternate mode of operation by touch, voice control or gesture input that conforms to 307.6.1 or 307.6.2, as applicable.

Advisory 307.6 Non-Mechanical Controls.  Examples of alternate modes of operation include touch screens, keyboards, virtual keyboards, and buttons.

Examples of non-mechanical controls that are touch operated include touch screens, touch pads, gesture input devices, and membrane keyboards.

Examples of non-mechanical controls that can be operated without physical contact are user interfaces that operate by voice or in-the-air gestures.

307.6.1 Touch Operation.  ICT with controls that are operated by touch shall conform to 307.6.1.1 or 307.6.1.2.

307.6.1.1 Alternate Controls.  Touch-operated controls that conform to 307.5 shall be provided.

307.6.1.2 Without User Vision.  A mode of operation for the controls that does not require user vision for interaction shall be provided.

307.6.2 Operation Without Physical Contact.  When ICT is designed for use without physical contact, a mode of operation without touch shall be provided that does not require user vision for interaction.