Syrinx Mobile SDK allows you to transfer small amounts of text between mobile devices using sound. The transfer of information doesn’t require the internet, a mobile phone network, or a Bluetooth connection – just a microphone and a speaker is enough. The maximum size of one message is 255 bytes. This is enough to send, for example, a link, a telephone number, or a typical SMS message. The transfer protocol is designed to function in a place with background noise and reverberation.