hi neil
after all those years things have changed alot, but the transponder is really easy now,
the main thing is the personal transponder, these are very small and powered by the receiver,and are normally stuck to the chassis or on top of the servo etc. they have a number that is unique to the transponder so that the race software will only pick that transponder to you,also when you go to other meetings all you have to do is book in with your number and thats it
there are two main types the AMB and the MRT transponders, AMB is about £70 new and the MRT about £45 new, if you are lucky you may be able to pick them up second hand.
hope this explains well enough
we sell the MRT type from the shop
xtreme
www.xtreme-rc.org.uk