Visual impairment - severe . Cognitive impairment . The operating pressure required to activate a key may be critical for some people. Unsuitable pressure may result in mis-keying, either through no contact or repeated operation, and it may even lead to muscle spasm where the user cannot readily release the key. A means of adjusting the return spring pressure or, alternatively, a range of keypads with differing operating forces, is required to meet the needs of these users.
Telephone features that make a difference .