Build a TTY Transmitter with CLUE to Send Text Messages Over a Public Line

TTY (Text Telephone) machines have been around for decades and were initially designed for the deaf, the hard of hearing, or speech impaired to use the telephone and communicate via text messages. Of course, to communicate, users required two TTY machines to send and receive messages, which was done by placing the handset onto a pair of acoustic cups located on top of the device. You could then type what you wanted to say using the keypad, which would convert the messages into five-bit audio tones in real-time, just as you would talk on the phone.

Cellphones all but killed those old TTYs, and with today's smartphones, there's no longer a need for the tech. That being said, it's still great to use that old tech and merge it with today's hardware, which is what John Park did by using his smartphone to relay text messages to a TTY machine via an nRF module. His CLUE Text Telephone Transmitter was designed using Adafruit's CLUE module, which packs an nRF52840 Bluetooth LE processor, a series of sensors (temp, motion, sound, etc.), and a 1.3-inch (240 X 240) IPS TFT display.

Park paired the CLUE development board with Adafruit's STEMMA speaker/audio amplifier, which is then placed into a receiver cup on the TTY machine. After a little coding using CircuitPython, he was able to send text messages to the machine via a smartphone (Android or iOS) and CLUE module, which translates the messages into five-bit signals that are pumped through the speaker into the machine in near real-time. While it may seem like a novelty, it could come in handy if cell towers are down, but that's only if the recipient has a TTY machine as well.