This project is very basic and doesn't perform any validation/checksum tests on the received data, but it does seem to be fairly reliable even with a small amount of background noise. The default tones used in this project are listed below: Transmission Start: 2000Hz Data Bit 1: 600Hz Data Bit 0: 800Hz Transmission End: 1500Hz Next Bit Confirmation: 1200Hz The transmission speed is determined by the TONE_LENGTH_MS value in the sender program. The receiver program is able to automatically adjust to any transfer speed because consecutive tones are never equal by design. Each tone has a duration of 50ms by default - this seems to be reliable in my testing.