I've heard on another forum of a club that switched their totally used AMBrc-clubtransponders for two sets of 10 MRT-pt's.
AMBrc-clubtransponders have a battery.
(MRT can switch these batteries also for you, if the batteries are at the end of their lives.)
The MRT-pt's have a power-wire, so now someone who uses one of their Clubtranponders will have to connect that powerwire to their receiver.
And to make things clear, they just gave every of their two sets a color, by spraying a fluorescent color on them. Whenever the color has weared out to much, they just spray some new paint on them. These pt's don't have to be beautifull, but usefull!
It works like a charm and was MUCH less expensive then a new set of AMBrc-clubtransponders (which, AFAIK, are much more expensive then regular AMB Clubtransponders).
If you wonder ... I have no connection with MRT, except for the fact that I bought an MRT-pt, but I contacted Tony from MRT by phone when I was looking for info for an RC-club I knew that were looking into the possibility to buy MRT-pt's to replace their AMB20-system.
SO I digged into the matter and phoned MRT a couple of times.
Also, there are some threads about MRT-pt's on the RCtech.net-forum