Identifiers measure differences in radiation emission energies to determine the specific type of radioisotope present. They are typically used to identify unknown radioactive sources. They are larger than detectors and dosimeters, and are routinely found in the form of a rectangular box with a handle on top. Several differing detection technologies are utilized within this application category including scintillation crystals (CsI or NaI) and semiconductors (CZT or germanium). Scintillators typically identify radioisotopes faster than semiconductors, while semiconductors are more accurate for the identification of mixed signatures. Identifiers range in price, and are routinely much more expensive than dosimeters and detectors.