A Coded identification crystal is a sub-dermal implant injected into all high-ranking Earthdome personnel as a precaution against kidnapping. The crystal emits a very low-level signal that can be detected over a short range by specialised hand held scanners. In 2259, ESID agent Derek Cranston attempted to track the fugitive Doctor Everett Jacobs on Babylon 5, providing B5 Security with the ID scanners to track down Jacobs.