what I guess what I am describing is called. I have a Echomaster. I was curious about transponders, as we had a Minitransat 6.5 sailor at our club for a few days and she used an AIS and a transponder, but I didn't get the brand. Of course she had no radar on her boat. I have radar with a guard alarm hooked up to a home burglar alarm horn (it will wake the dead when it goes off) and a C.A.R.D system, but you can't use both at the same time. After much debate I just ordered an AIS unit. I know that the Vende Globe guys use transponders, that I know. I don't know if anyone sells the SeaMe unit in the US, but it sure is expensive, plus I'm not clear if you can use you own radar when it is on.