"I agree, at 5V driving the transducer is likely just as good from the Arduino directly. There impedance is about 1K at 40KHz. I wasn't thinking of current, but the voltage.
"David, that's an interesting suggestion. I am a bit busy for the next few weeks to try it, but I think the ability to calculate position would be extremely useful even for Earth-bound robots. I have several sets of very low-cost ultrasonic…"
"I assume you're concerned about telling the difference between direct sound and a reflection of a wall?
It is probably a combination of techniques, including, at least:
1. If only one device at a time shouts, and they leave a big gap every receiver…"
"There was a neat technique explained in a recent Scientific American on Robotics (May 2008, "An Army of Small Robots", by R Grabowski, L E Navarro-Serment and P K Khosla, This looks like a plausible reference:…"