You don't race more than 2 microsizers.... there are only two frequencies.... If you want to race more cars you need more frequencies... and you get more frequencies by buying Japanese or Australian models...
There are 6 total frequencies for the TOMY produced Bit/Micro Line...
check out this thread... it should explain it..
http://tinyrc.com/forums/showthread.php?s=&threadid=899
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