http://support.mylaps.com/kb/en/b2b/...l_vJan2010.pdf
On page 5 of the manual the loop shows are R at the center of the loop. That is a resistor you can buy and make your own loops. For our track, we tape the loop to a piece of carpet, then flip it over, and tape it to the carpet we use for racing. You can also make a bridge.
Hope this helps