What is software RTT and TTY, and hardware TTY?

In the context of iPhones or mobile devices, RTT and TTY refer to two different features related to accessibility and communication:

1. RTT (Real-Time Text): RTT is a communication feature designed to assist individuals with hearing or speech disabilities during phone calls. It allows users to send text messages in real-time during a phone call instead of speaking. This text-based communication can be useful for people who are deaf or hard of hearing and enables more accessible and effective phone conversations. Both parties in the call need to have RTT-capable devices or software for this feature to work.
2. TTY (Teletypewriter): TTY is an older technology that predates smartphones but is still supported on many modern devices, including iPhones. It's also designed to assist people with hearing or speech impairments in phone communication. TTY devices, often called teletypewriters or TDDs (Telecommunications Devices for the Deaf), allow users to type messages back and forth during a phone call. TTY devices are typically connected to the phone line or a mobile device via specialized adapters.

Set up RTT and TTY

• Go to Settings  > Accessibility.

Please see the pic below which is self-explanatory