# CLUE Text Telephone Transmitter ## Overview https://youtu.be/z2ht4x-8qz4 The TTY machine (a.k.a., Teletype/textphone/Minicom) is a communications device similar to a teleprinter that is used to send text messages over the public switched telephone network. The TTY was developed in the 1960s to assist deaf and hard-of-hearing users in communicating over the telephone system. It consists of a keyboard, display, and acoustic coupler for a phone handset (some also included a small continuous roll printer or interface for external printers). The TTY converts typed characters to audio signals which can be sent over the phone system to TTY machine on the receiving end, where those audio signals would be converted back to text for display. The TTY was supplanted in the 1990s by modern services such as instant messaging on computers and texting on phones (as well as video calls and video relay services for sign language use) but the technology is interesting to study, and in fact still works on some phone exchanges. In this guide we'll take a look at how the TTY uses audio tones to communicate and build our own transmitter with a CLUE capable of sending messages to a TTY machine, both in standalone mode and in Bluetooth LE mode with messages being sent from iOS or Android. https://youtu.be/vsi7gwKwP-U ## Parts ### Adafruit CLUE - nRF52840 Express with Bluetooth® LE [Adafruit CLUE - nRF52840 Express with Bluetooth® LE](https://www.adafruit.com/product/4500) Do you feel like you just don't have a CLUE? Well, we can help with that - get a CLUE here at Adafruit by picking up this sensor-packed development board. We wanted to build some projects that have a small screen and a lot of sensors. To make it compatible with existing projects, we made... In Stock [Buy Now](https://www.adafruit.com/product/4500) [Related Guides to the Product](https://learn.adafruit.com/products/4500/guides) ![Animated GIF showing CLUE board displaying data from the many on-board sensors.](https://cdn-shop.adafruit.com/product-videos/640x480/4500-04.jpg) ### Adafruit STEMMA Speaker - Plug and Play Audio Amplifier [Adafruit STEMMA Speaker - Plug and Play Audio Amplifier](https://www.adafruit.com/product/3885) Hey, have you heard the good news? With Adafruit STEMMA boards you can easily and safely plug sensors and devices together, like this **Adafruit STEMMA Speaker - Plug and Play Audio Amplifier**. Like the name implies, it's got a class D audio amplifier on board, and our... In Stock [Buy Now](https://www.adafruit.com/product/3885) [Related Guides to the Product](https://learn.adafruit.com/products/3885/guides) ![Top view of a black speaker breakout board connected to a round microcontroller via alligator clips. A music note animation emits from the speaker.](https://cdn-shop.adafruit.com/product-videos/640x480/3885-05.jpg) ### USB cable - USB A to Micro-B [USB cable - USB A to Micro-B](https://www.adafruit.com/product/592) This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller Approximately 3 feet / 1 meter long In Stock [Buy Now](https://www.adafruit.com/product/592) [Related Guides to the Product](https://learn.adafruit.com/products/592/guides) ![USB cable - USB A to Micro-B - 3 foot long](https://cdn-shop.adafruit.com/640x480/592-01.jpg) Info: - [Next Page](https://learn.adafruit.com/clue-teletype-transmitter/tty-fundamentals.md) ## Featured Products ### Adafruit CLUE - nRF52840 Express with Bluetooth® LE [Adafruit CLUE - nRF52840 Express with Bluetooth® LE](https://www.adafruit.com/product/4500) Do you feel like you just don't have a CLUE? Well, we can help with that - get a CLUE here at Adafruit by picking up this sensor-packed development board. We wanted to build some projects that have a small screen and a lot of sensors. To make it compatible with existing projects, we made... In Stock [Buy Now](https://www.adafruit.com/product/4500) [Related Guides to the Product](https://learn.adafruit.com/products/4500/guides) ### Adafruit STEMMA Speaker - Plug and Play Audio Amplifier [Adafruit STEMMA Speaker - Plug and Play Audio Amplifier](https://www.adafruit.com/product/3885) Hey, have you heard the good news? With Adafruit STEMMA boards you can easily and safely plug sensors and devices together, like this **Adafruit STEMMA Speaker - Plug and Play Audio Amplifier**. Like the name implies, it's got a class D audio amplifier on board, and our... In Stock [Buy Now](https://www.adafruit.com/product/3885) [Related Guides to the Product](https://learn.adafruit.com/products/3885/guides) ### USB cable - USB A to Micro-B [USB cable - USB A to Micro-B](https://www.adafruit.com/product/592) This here is your standard A to micro-B USB cable, for USB 1.1 or 2.0. Perfect for connecting a PC to your Metro, Feather, Raspberry Pi or other dev-board or microcontroller Approximately 3 feet / 1 meter long In Stock [Buy Now](https://www.adafruit.com/product/592) [Related Guides to the Product](https://learn.adafruit.com/products/592/guides) ## Related Guides - [Adafruit STEMMA Speaker](https://learn.adafruit.com/adafruit-stemma-speaker.md) - [Introducing Adafruit CLUE](https://learn.adafruit.com/adafruit-clue.md) - [¡Bienvenido a CircuitPython!](https://learn.adafruit.com/bienvenido-a-circuitpython-2.md) - [CircuitPython BLE Advertising Beacons](https://learn.adafruit.com/circuitpython-ble-advertising-beacons.md) - [CLUE Altimeter](https://learn.adafruit.com/clue-altimeter.md) - [Yoga Pose Chime](https://learn.adafruit.com/yoga-pose-chime.md) - [PyLeap CLUE Custom Conference Badge](https://learn.adafruit.com/pyleap-clue-custom-conference-badge.md) - [CLUE Step Counter](https://learn.adafruit.com/clue-step-counter-st-lsm6ds33.md) - [Glowing Bottle Castle and Capacitive Touch Piano](https://learn.adafruit.com/glowing-bottle-castle-and-capacitive-touch-piano.md) - [Clue And MagTag Pep Talk Generator](https://learn.adafruit.com/clue-and-magtag-pep-talk-generator.md) - [Adafruit LSM6DS33 6-DoF IMU Breakout](https://learn.adafruit.com/lsm6ds33-6-dof-imu-accelerometer-gyro.md) - [CLUE case](https://learn.adafruit.com/clue-case.md) - [CircuitPython CLUE I Ching Caster](https://learn.adafruit.com/clue-i-ching-caster.md) - [CircuitPython BLE Libraries on Any Computer](https://learn.adafruit.com/circuitpython-ble-libraries-on-any-computer.md) - [BLE Thermal "Cat" Printer with CircuitPython](https://learn.adafruit.com/ble-thermal-cat-printer-with-circuitpython.md) - [CLUE Light Paint Stick with CircuitPython](https://learn.adafruit.com/clue-light-paintstick.md) - [Digital Nose Milk Freshness Checker](https://learn.adafruit.com/digital-nose-gas-sensor-milk-freshness-checker.md)