Time Delay Percussion Igniter (TDI XL) Product Description The TDI XL is used for igniting time delays. Support hardware and assembly is not required. Backwards assembly is eliminated by the geometric interface. Our TDI XL assures reliable ignition under harsh environments and variable gap/alignment conditions. To protect and preserve the explosive primer for extended life and high reliability under harsh conditions, we provide a one piece, hermetically sealed enclosure.