RTT can refer to a few different terms:
Real-time technology refers to technology that permits a user to receive data during the actual time a physical process occurs. This is known as real time, and it is measured in milliseconds or microseconds. Real-time technology is used for entertainment purposes such as live streaming videos and sound, but is also used for critical applications. For instance, an automatic pilot uses RTT to immediately respond to data on changing flight conditions or positioning. A nuclear power plant uses it to have real-time information about the critical areas of the plant for safety. Space flight computers use it to respond instantly to changing atmospheric conditions.
Round-trip time, also known as round-trip delay, refers to the time required for a signal to travel from the source to the destination and back. The signal is typically a data packet, and the time includes the propagation times for the paths between the two communication endpoints. The RTT between a network and server can be determined using the ping command.
Real-time text is text instantly transmitted while it is being typed or created, with characters being sent immediately once typed and displayed to the receiving person(s) in real time. In this way, RTT has a conversational directness and interactivity as voice does. It can be used as a stand-alone feature or in combination with other features such as voice telephony and video conferencing. Using all three simultaneously is called total conversation.
This feature is especially useful for those who are deaf or hard of hearing because it can replace Text Telephone technology.