First, look on the box that came with your 
transmitter.  There should be a nine-digit number 
there.

  If you don't have the box, your nine-digit
number is most likely the number on the back
of your clicker preceded by 000.  This is so
likley to be true that you can go ahead and
register making this assumption.  But you will
have to check this assumption when you actually
use your clicker in class to answer a question.

  Here's how to do that check.  When you use 
you clicker to answer a question, look at the 
PRS screen and watch for your number.  If you 
see exactly the six-digit number on your clicker, 
then your PRS ID is

                 000XXXXXX 

where XXXXXX stands for the 6-digit number on 
your clicker.  On the other hand, if the number
you see is 1XXXXXX, then your PRS ID number is

                 001XXXXXX

If this happens to be the case for your clicker
(the chances are about 1 in 100), then you will
need to reregister your clicker.  Thanks.  GBA.

P.S.  There are a few transmitters with only
      a 4-digit number!  Follow the same rules
      as above.  Your PRS ID is either

        00000XXXX    or    00001XXXX

      You can determine which is correct by
      watching the screen.