193.136.16.239@IDITE.UMINHO.PT wrote:

>The project that we are developing is a time control of a kart racing.
>The first option was the use of transponders for Kart identification,
>but the problem of more then one kart may pass through the finishing
>line at the same time exists.
>The other option was the use RF emiters in the kart's.
>I appreciate that you send me your opinion to this problem, and we
>are open to other sugestions. Please send me also were we can find
>FAQ's, Sites and supplier address.

  Have you thought of putting a simply bar code on the top of the karts?  A
bright light and slit for the light to pass through would eliminate the need
for a len to focus the light.  A photodiode with Automatic Gain Control
should be sufficient to recover the digital signal.  It's a lot of work, but
you'll have fun.

  -- Hank