There are a few key differences between RTT and TTY:
-TTY is a text-based communication system that requires a special TTY machine in order to work. RTT, on the other hand, is a real-time text communication system that can be used without any special equipment.
-TTY is a slower communication method than RTT, as it can take up to a minute for a message to be sent and received. RTT, on the other hand, is a much faster communication method, with messages being sent and received almost instantaneously.
-TTY is a unidirectional communication system, meaning that only one person can send a message at a time. RTT, on the other hand, is a bidirectional communication system, meaning that both people can send and receive messages at the same time.