[CQ-Contest] WPX question

[Valeri Stefanov]

Hi Fellow contesters,

In the rules for WPX 2003 for newly introduced category M/2 they say a unique transmitter identifier must be kept for each TX. Can anyone explain what the animal is this ?  Guess such indentification  it is done automatically by the software used, but this is not clearly said in the rules ?

73's de Wally LZ2CJ (LZ8T) , team member LZ9W , YM3LZ