A component of a Guth 10-4D, 2100, and later simulator that gives a digital indication of simulator temperature. This component SHOULD have its own maintenance and calibration history. The OPP have been using high quality reference thermometers to verify these digital thermometers about every 6 months, other police services may not do it at all. Some erroneously use a Guth NIST certified mercury thermometer (which reads to .1 degree C) to verify a simulator digital thermometer that reads to .01 degree C.