Universal TTY/TDD devices for robust text and data transmission via PSTN and cellular phone networks

A communications system comprising:

• a plurality of text telephone TeleTYpe (TTY) devices, each including a modem that supports at least one of the protocols covered by the ITU-T V.18 standard and a new protocol having at least one of a) a higher reliability than the transmission protocols covered by ITU-T V.18, for connections that include digital cellular networks;
• and b) a bit transmission rate higher than 50 bits per second;
• and
• at least one signal adaptation server for converting messages from a protocol of one of the plurality of TTY devices to a protocol of another of the plurality of TTY devices.

A method for communicating text messages between first and second TeleTYpe (TTY) devices over a telecommunications network, wherein the first TTY device supports the transmission protocols covered by ITU-T V.18 and supports a new protocol having at least one of a) a higher reliability than the transmission protocols covered by ITU-T V.18, for connections that include digital cellular networks;

• and b) a bit transmission rate higher than 50 bits per second, and also the transmission protocols covered by ITU-T V.18, the method comprising the steps of:
• determining which transmission protocol(s) the second TTY device supports;
• determining whether a digital cellular network in the telecommunications network is connected between first and second TTY devices;
• when a digital cellular network is connected between the first and second TTY devices, transmitting the text messages over the digital cellular network using the new protocol;
• when a digital cellular network is connected between the first and second TTY devices and the second TTY device does not support the new protocol, translating the text messages between the new protocol and one of the transmission protocols covered by ITU-T V.18 and supported by the second TTY device;
• and
• when the first and second TTY devices each support the new protocol, transmitting the text messages across the telecommunications network using the new protocol.