All about transponders

The transponder is used to identify a person in a race by sending a unique digital code when required to an RFID reader. Transponders come in all shapes and sizes and work at all kinds of frequencies. RFID Race Timing Systems use two specific type of transponder that are perfect for sports timing. Both are passive transponders meaning they do not use a battery to transmit their signals to a reader.

Low Frequency Half Duplex 134Khz

Developed by Texas Instruments in 1993 this transponder has been extremely successful in animal identification and sports timing. Excellent reliability and readability under field conditions. The transponders are hermetically sealed in a glass capsule and can be read under water if neccessary. The downside to low frequency is that only one transponder code can be read by a reader at any one time. Sometimes a transponder may fail to read if two transponders are in the same read field. However techniques are used to avoid this problem by 'locking on' to the closest transponder and using multiple receiver loops attached to multiple reader circuits.

UHF Transponders (868 - 950MHz)

These type of transponders generally use radiated electrical energy to transmit their information to a reader antenna and the read distances are substantially more than for low and high frequency transponders that use inductive coupling. A great deal of research and development has been devoted to UHF technology because the transponder (or tag) is usually low cost consisting of thin flexible copper antenna and tiny integrated circuit the size of a grain of sand. These transponders can be read in large numbers at the same time using anti-collision algorithms. These algorithms were further enhanced with the adoption of EPC Class 1 Generation 2 protocol amongst the world leaders in tag and reader manufacture. RFID Race Timing Systems had evaluated many forms of UHF tags and readers and until the Battery Assisted Passive (BAP) tag, we did not see a reliable future for this technology. However things have changed and the latest readers and BAP have been brought together in our world leading Ultra System.

//back to top

How many athletes can I time?

This question is only relevant to the level entry Dual Antenna System which has just two receive antennas. We do not recommend using just one of these systems in races bigger than 200 competitors due to the increased risk of tag collision. The HDD and Ultra Systems can handle as many runners as you can fit across the antenna mats. This is typically around 700 runners per minute over a 4m wide mat.

//back to top

Will the RFID Race Timing System be out of date in several years?

The low frequency transponders are still the benchmark for sports timing. Where transponders must be worn on the ankle (such as triathlon) low frequency transponders are the most reliable because they can read through most objects including water. The low frequency transponder will be around for many more years because there are very few other systems that work as well for triathlon.

Even with the advent of new UHF technology, our HDD System continues to be a great performer for all types of events. A robust timing platform with the economy of re-usable transponders.

//back to top

Will UHF RFID eventually be used in every type of event?

It is unlikely that just one type of RFID technology will time all events from running to biking and triathlon. Certainly the UHF tags we see today are lower in cost and have a lot of potential in terms of read rates and range. However the disposable tag is not for everyone and in smaller races, the reusable transponder is still very economical and not difficult to claim back after the race. The advent of the BAP UHF tag has greatly improved the performance of UHF timing systems and one day we may see this type of tag used in events like triathlon.

//back to top

Is there after sales backup?

Definitely. We not only have expertise in building the best timing systems, but also in timing events themselves. RFID Race Timing has been involved in timing triathlons and swim events for over 8 years. We understand the requirements for completing the task of timing your event - from entering race competitors, to publishing results in the right format and on the best medium. Any problems with systems will be rectified quickly and efficiently, even if we have to send over a replacement system quickly in case you have an event to time while your own system is repaired. Service plans are available after the initial 1 year warranty.

//back to top

Can you modify the race software for our application?

Yes. If your event requires a particular format for data capture or results presentation, we can often work closely with our software developers to modify current software packages. Many of these improvements flow on in the form of software upgrades to current owners of the system.

//back to top

What is the difference between low and high frequency transponders?

We use low frequency (134khz) transponders and readers which generally are the standard used for sports timing. They offer good read range, read focus of antennas and can penetrate most mediums other than metal. The 134khz system is half duplex meaning that only one transponder can be read at any given time over a antenna mat. However, if transponders are slightly staggered as they cross over the mat, they will both be read in the correct sequence. This is actually an advantage since it means that the correct order of transponders crossing the mat is recorded. Sprint finishes can be easily and accurately separated to 0.1 second resolution. The much more common high frequency transponders tend to be cheaper and full duplex meaning that many transponders can be read at the same time by one antenna. This type of system is favoured for tracking goods in a warehouse (ie. Walmart). This is because the system is cheaper, transponders are expendable and most importantly, all the information that is required is whether the item or goods are in the general proximity of the antenna and RFID reader. Read order is less of a concern other than on a checkout where the read range is generally quite short (less than 12 inches). Most high frequency transponders operate at 13.56 MHz and the bulk of research centre's around UHF systems. Some of the claims from the UHF reader manufacturers seem impressive and RFID Race Timing has evaluated the latest UHF reader for certain sports timing applications. There are a few examples of high freqency RFID timing systems in the world but the major feedback is that they lack the accuracy of the low frequency systems. Active high frequency transponders give better reliability but they are expensive. To read more about RFID technology we suggest visiting RFIDusa which can explain many of the technical terms used in RFID.

//back to top

What is the difference between Ultra and Chronotrack?

Both systems use UHF Generation 2 readers working in the same band for the country of deployment. The systems differ in the type of antennas used and most strikingly, the position of the transponder on the athlete. With Ultra there is no need to put anything on the shoe lace and worry about the athlete making mistakes with putting the tag on. The BAP tag used in Ultra sticks to the back of the existing race bib making the timing process more efficient and reliable. You only need to miss the finish time of 1% of runners to receive 200 angry emails post race. Many of these runners will have made an innocent mistake attaching their shoe tags on the Chronotrack system.

//back to top

What is Tag Collision?

In RFID systems there are times when two or more transponders may simultaneously send their signal to a reader. If the signal frequency of these two transponders is the same and they are less than 8 centimeters apart, then the reader will have difficulty separating the information and neither transponder will be read. This is called a 'tag collision'.

The TI 134kHz transponder that RFID Race Timing Systems uses is half duplex. This means that the transponder communicates in one direction. The advantage of half duplex transponders is that they can be read from a greater distance away from the reader antenna. To minimize issues with tag collision, our systems read at 20 times per second. The new HDD system improves things even more by installing numerous readers and antennas within the mat matrix. With 16 readers all reading 20 times per second, it becomes virtually impossible to miss a transponder due to tag collision. The HDD was designed to handle all athlete densities and in particular, those seen at the start line of large fun runs.

//back to top