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The genius of TDD is that nothing happens.

RTT, or real-time text, is a mode where people can call deaf and hard-of-hearing people who use a TDD device.

TDDs make a unique sound, so it was easy to know when another TDD user was calling my parents; I would simply place the phone’s receiver on the TDD and tell my parents the call was for them.

Assistance is available in more than 150 languages, and TDD/TYY access is provided for voters with hearing impairments.

The network, on the 2600 MHz TDD frequency, will be rolled out using technology from Nokia and Ericsson, Cyfrowy Polsat said.