itolond:
In short are you suggesting the 'physical' transmission via acoustic serviced via speakers and then 'develop' a code protocol to interpret theses?so in a TX/RX -TX/RX scenario would need to mount similar units?
Addendum: I was looking to setup a buoy with comms to the 'on-shore' device and then retrans /recieve from underwater unit/s
You can adopt TV remote control, you need to lower transmitting frequency, divide it by 2 ,so will fit in audio range.