36 CFR Part 1193 Telecommunications Act (Section 255) Accessibility Guidelines

Paragraph (d)

TTY Connectability

1. Acoustic coupling is subject to interference from ambient noise, as many handsets do not provide an adequate seal with TTYs. Therefore, alternate (non-acoustic) connections are needed. Control of the microphone is needed for situations such as pay-phone usage, where ambient noise picked up by the mouthpiece often garbles the signal. For the use of voice carry-over, where the person can speak but not hear, the user needs to be able to turn the microphone on to speak and off to allow them to receive the TTY text replies.

2. A TTY can be connected to and used with any telecommunications product supporting speech communication without requiring purchase of a special adapter, and the user is able to intermix speech and clear TTY communication. The most common approach today is to provide an RJ-11 jack. On very small products, where there may not be room for this large jack, a miniature or subminiature phone-jack wired as a "headset" jack (with both speaker and microphone connections) could be used as an alternate approach. In either case, a mechanism for turning the phone mouthpiece (microphone) on and off would reduce garbling in noisy environments, while allowing the user to speak into the microphone when desired (to conduct conversations with mixed voice and TTY). For equipment that combines voice communications, displays, keyboards and data communication functions, it is desirable to build in direct TTY capability.