Ambient Weather WS-21 Wireless 8-Channel Thermometer with Two Remote Sensors Simple to read, simple to use, and affordable, the WS-21 includes an indoor thermometer in the console and can remotely read and update up to eight remote thermometer sensors at the same from the large digit, uncluttered jumbo display. The WS-21 includes two remote thermometers and six additional sensors can be added (F007T, F007TP, F007PF) for comprehensive monitoring. Each remote sensor includes dip switches for channel selection and units of measure (degF vs degC). The sensor search mode allows you to re-sync sensors without removing and re-inserting batteries. Optional calibration is provided for the upmost accuracy, Although calibration is optional and not required, the purpose of calibration is to fine tune or correct for any sensor error associated with margin of error and inevitable sensor drift.