Which device allows speech and hearing impaired citizens to communicate over the phone?

The teletype is a specialized communication device designed to assist speech and hearing impaired individuals in communicating over the phone. It operates by converting typed text into a converted format that can be sent over telephone lines. Users type their messages on a keyboard, and the device sends this information to another teletype machine, where it is printed out or displayed for the recipient, allowing for effective communication without the need for vocal speech.

Other devices listed, such as headsets and standard telephones, facilitate traditional voice communication, which would not be effective for someone with speech or hearing impairments. Two-way radios may be used for communication in certain contexts but do not have the specific features that make a teletype effective for deaf or hard-of-hearing individuals. Thus, the teletype stands out as the most suitable option for enabling phone communication for speech and hearing impaired citizens.