How a passive chip is read
A passive UHF chip has no battery. As the athlete crosses, the reader’s radio field powers the chip, and the chip reflects its number. TMK Platform Ⅲ uses ISO 18000-6C and EPC C1G2 at 865–868 MHz and 902–928 MHz.
How the line records the crossing
The folding mat lies on the line, with the antenna and feed inside. It reads about 1.5 m either side of the line, with the chip upright or flat. The decoder stamps the number and that stamp is the split.
Why road races use passive chips
The chip sits on the bib or the lace. It needs no battery and no charge-up, which suits marathons, trails and fitness tests.
How this differs from active timing
An active chip has its own power and transmits. A passive chip has no battery: the reader powers it at the line, and the chip reflects its number.
TMK’s passive timing chain
TMK Platform Ⅲ is the UHF decoder. The folding mat is the antenna on the line. Together they read the chip and cover the line.