Central Division Sports Car Club of America

Many of the regions in Central Division are requiring transponders for Timing and Scoring at their races. Transponders may be available for sale or rent at the track, but you should check with the Chief of Timing & Scoring or the Chief Registrar before the event to be sure.

To purchase your own transponder, contact AMB directly at www.amb-it.com and navigate to their online store.

Frequently Asked Questions about Transponders

by Anne Kumor, Milwaukee Region

What needs to be done to the track?

There's a "loop" embedded in the track, hopefully at the start/finish line, and definitely at the timing line. As each transponder (TX) crosses the loop, it is sensed, and a time and the transponder identification are sent to the timing software. The software calculates the lap time based on the previous “passing” time.

Where do I put the transponder?

A TX is mounted in a bracket on the car, vertical to the track, not more than 2 feet from the track, without any carbon/composite material between the transponder and the track. As the car passes over the loop, it sends a signal to the loop with its TX number. In addition (PAY ATTENTION – THIS IS NOT IN THE INSTALLATION INFORMATION FROM AMB) the transponder sends its signal in a cone shape, opening up towards the track, so if there is any metal in front of or behind the transponder, its signal will be reduced, resulting in a form you will receive at black flag. Unlike the diagram supplied by AMB with the TX, the opening should be at least 4 inches in diameter, with the TX mounted flush with the bottom of the metal. Some drivers, concerned about debris “kicking up” at the TX, have installed a plate of clear Plexiglas across the opening and have the TX flush with the Plexiglas. This has been observed to work well and does not result in any signal loss.

Where do I wire in my transponder?

A hard-wired TX draws not more than 10 milliamps. It is best to wire it into the master switch, so the unit is sending as long as the car is “on”. When the car is off, the TX is not sending. If you have the TX on a separate switch and forget to turn it on, you may not be timed.

How does this transponder get the information to Timing & Scoring?

The signal that is generated as a transponder crossing the loop is sent to a decoder unit that is plugged into the loop on one side, using a coax cable, and on the other end a serial cable connects to the timing computer. The decoder translates the many TX signals received as the car crosses the loop with a time (to the .001 second) to something that the AMB software understands, and sends it into the program. The program keeps track of the passing order of the cars, the times, the number of times the TX (and hopefully the car) has passed over the line (number of laps completed), and automatically subtracts this passing time from the previous passing time to get the lap time. In case a car passes the loop without giving a time, we have people writing down all the car numbers as they go by anyway, and we can see which car is not registering a "pass" (completed lap). The software also registers “hits” and “strength” that, when low, indicate there is metal/composite material blocking the signal as described above.

The difference from our current Timing & Scoring system is: we use a photocell timing light that has a "beam" that crosses the track. When a car breaks the beam, our timer records the time (to the .001 second) and sends it to our computer, we in T&S associate the car number with the time, and the software we use does all of the same other things described above for the AMB system.

Why can't two cars in different race groups use the same transponder?

Using AMB, there is one database for all participants in an event, not separated into race groups. The transponder number is the single unique identifying signature for all cars as they pass the loop - all other information like driver, number, class, etc. are associated with that one transponder. It is not possible to associate two different drivers or cars with the same transponder. This makes it impossible for two cars running in the same event to share the transponder.  Please note that when a Restricted Regional runs with a National Race weekend, we will load a separate database for the Regional, so that a TX can be shared between exactly 2 cars in two different “events” (the Regional is a separate event than the National). If there is a double event, and the same car or transponder is entered by different drivers for each of the EVENTS (one for the first day and the other for the second day), there are two separate databases, and the software is happy.

How can I see if my transponder is working before I go on the track?

The hard-wired transponder includes an LED that is solid green if the unit is sending a signal. A rechargeable transponder has a flashing green indicator that blinks once for every day of charge left (4 blinks = 4 days, 3 blinks = 3 days, etc). When a rechargeable transponder starts to flash amber the rechargeable unit has less than 24 hours left on the charge and needs to be recharged. Also, at some events a hand-held tester will be available at the scales when they are open as in the event schedule, to run under the car at ground level. This unit indicates if the signal is being sent, however, the hand held unit is not able to detect the signal interference due to metal blocking the signal. This can only happen on track, at speed. Yes, the car’s speed does affect the loop sensing the TX – the faster the car is going, the shorter time the TX spends over the loop sensing area.

Where can I see the transponder times?

The TX times are posted with the results for each session. The format may be different that what you have seen in the past. In addition, visitors are always welcome in Timing & Scoring to see the system in action or to ask questions about a problem that was reported.

Where do I put the transponder on my car?

On anything with fenders, AMB recommends in the front wheel well, as long as it is protected as well as possible from body damage (parts flying off). On cars without fenders, find a "safe" place near the front of the vehicle. It cannot be more than 2 feet from the track surface, and can have no metal or composite material between it & the track. It needs to be mounted vertically to the track surface. When in doubt, ask the Tech inspectors for suggestions, or ask a fellow competitor with a similar car.

Since we will likely never use the transponders for scoring (finish position), it is not crucial to have the exact same position in all cars in a class. The timing for each lap will begin the first time the transponder passes over the loop, and the lap time will be calculated based on the difference in time until the next time the transponder passes over the loop. On each successive lap, the lap time will be consistent with the "base time" tracked from the passing on the previous lap. The final finish position will still be done visually, as we have always done with close finishes (2 cars passing the finish line at "the same time"). I hope this answers your question & makes sense. To use the transponder for scoring (finish position), the SCCA GCR would need to specify a particular placement for each vehicle.

Is there a "spec" location for mounting the transponder?

NO. Since transponders will only be used for timing, but not scoring, there is no spec location. They only need to be mounted within the mounting guidelines described above, such that the signal can reach the loop in the track.

What do I do if I get a transponder form from Black Flag?

There is a problem with your transponder that you need to fix. You received the from because the TX software noted a problem: Metal below the TX (box 1),  metal in front of or behind the TX (box 2), an unknown problem that sometimes causes the TX to not be sensed when crossing the loop (box 3), at the start of the session the TX was sensed fine, no metal interference, but then it simply stopped being sensed (box 4), you did not have any TX sensed (box 5), or the unit needs to be recharged (box 6). Look on the back for a diagram that describes how the TX is sending and the loop is receiving the signal, if either box 1 or 2 is checked.

Why does T&S still make such a big deal about the number on my car?

When cars are on track, T&S still needs to visually confirm that as each car crosses the timing line, that it is the car the transponder is associated with. Also, corner workers call in car numbers;  course marshals look for car numbers;  pit, paddock and grid workers look at car numbers;  starters, black flag and stewards look for car numbers to identify a car.  Numbers must be clear, contrasting, and meet the approval of the Chief of Timing & Scoring, as per the GCR. Some things don’t change.