I recently had the opportunity to try out the Airwire 900 system when a fellow modeler ask my help in installing Airwire in three of his engines. I was more than happy to help as I was interested in the prospect of sound and battery operations.
My way of describing Airwire is to say it is battery operated wireless DCC. In essence the Airwire Converter Board is a "command station" and the two wires from the converter to the decoder are the buss. A T5000 or T1300 transmitter is used to "talk" to the converter board. A T5000 transmitter is necessary to program the converter board. After programming either transmitter can be used. All normal DCC functions are present from addressing the engine to sound and lights.
I converted a 2-8-0 steam engine, a Alco FA/FB unit and a Interurban. Pictures of the Alco follow. I am quite pleased with the operations and will eventually convert one of my HO F7A/F7B units.
The size of the CONVRTR-15 board plus a DCC decoder requires a lot more space than the DelTang receivers I have been using so it will not fit many of my engines.
In this install I removed the motor and drive gears from the B unit and installed a 1200mah two cell (7.4 volt) battery with a battery protection circuit, a Pololu 12 volt step up regulator, CONVRTR-15 board, charge jack and switch. A two wire connector feeds power to the A units sound decoder. Install was simple and it runs great. The owner says the engine ran nowhere near as well before.