36 CFR Part 1194 - Information and Communication Technology (ICT) Final Standards and Guidelines (with amendments issued through Jan. 2018)

412.8 Legacy TTY Support.

ICT equipment or systems with two-way voice communication that do not themselves provide TTY functionality shall conform to 412.8.

412.8.1 TTY Connectability.

ICT shall include a standard non-acoustic connection point for TTYs.

412.8.2 Voice and Hearing Carry Over.

ICT shall provide a microphone capable of being turned on and off to allow the user to intermix speech with TTY use.

412.8.3 Signal Compatibility.

ICT shall support all commonly used cross-manufacturer non-proprietary standard TTY signal protocols where the system interoperates with the Public Switched Telephone Network (PSTN).

412.8.4 Voice Mail and Other Messaging Systems.

Where provided, voice mail, auto-attendant, interactive voice response, and caller identification systems shall be usable with a TTY.