Functions and Features

It is important to remember the distinction between product functions and product features.  Functions are the “product’s answer to the set of user tasks”; features are the “user tools” inherent in the product used to perform the functions (Wood, 1995).  Placing a telephone call is a function; the dial tone and the touch-tone keypad are features used to accomplish the function.  Product Types have different sets of functions, and each Model within a Type accomplishes its functions through potentially different features.

This Report focused on features.  Across all Product Types, a small but effective set of features currently address the Guidelines.  The lists below include all features found on products we analyzed.  Note that our analysis did not include in-depth examination or testing.  For example, a product that claimed to have a “large, easy to read display” was not measured or otherwise examined for this quality, in the absence of any standards of legibility and testing protocols.  There is more information on this problem in the Recommendations.

The first list is made up of common features; the second, uncommon.  We use the term “common” to mean not necessarily ubiquitous, but found often enough on Models of the relevant Product Types to enable a reasonably well informed and resolute consumer to find a product with that feature. Common features were those found on at least twenty Models total from at least two Product Types.  Uncommon features were in fact found on fewer than ten Models.

Note that some common features are common only to some Product Types and may not be commonly found on other Product Types.  For example, dialed number display is found on all wireless phones and some cordless phones, but few residential wireline phones.  Carrying over features from one Product Type to another may be a relatively easy way of expanding the number of products that address the Guidelines.

See the Trace Center’s Reference Design, which describes a set of access features that is designed to cover every Guideline.

Common Features

Headset or headset jack (usually with audio cutoff).

Volume control.

Tones indicating functions or status.

Adjustable ringer volume.

Hearing aid compatibility.

Vibrating alert.

Dialed number display.

Buffer dialing (entering digits, then activating a dial command).

Caller ID on call waiting.

Visual alert of status.

Illuminated or high-contrast controls.

Illuminated or high-contrast display.

Large display.

Variable signal tones.

On-screen operation and activity display.

Color coded controls.

Keys identifiable by touch (nib, shape, raised letters, etc.).

Controls grouped by function.

Large buttons.

Speed dial.



Any-button answer.



Stable and operable when placed on flat surface.

Simplified controls (compared to other Models).

Uncommon Features

Enhanced voice quality.


Composable signal tones

Zoom display. (A zoom display allows users to change the size of the characters.  For example, 4 lines of text can become 2 lines with characters twice as high.)

Speech synthesis announcement of functions, status.

Speech recognition controls.

Automatic redial (product keeps redialing until a connection is made).

User can dial 911 without dialing ‘9’ first (on PBX).

Infrared or radio frequency port.

Transfer number from Caller ID into speed dial.