Tyrone,
The machine that I saw, looked alot like my USN 58L in size. Very similar to what I use everyday, except the transducer was much different in that it had multiple crystals and they were mounted within the transducer at various angles. My understanding was the logic/programming in the machine's computer fired the signals in some particular order, and then it painted what it was seeing on the screen for you in realtime.
They claimed that by using this machine, they could inspect the wheels and axles for fatigue while they were still on the train(no disassembly required like with previous inspections methods).