The Automatic Phone-Out Freeze Monitor calls up to five programmed phone numbers when the temperature drops below 42 F (5.5 C). The keypad base unit quickly plugs into both the phone line and electrical outlet. An internal sensor continually monitors the temperature of your home, cabin or cottage. The Automatic Phone-Out Freeze Monitor calls five programmed phone numbers of your choice anywhere in North America and alerts with a built-in 110dB tone alarm that a temperature problem exists. The Keypad includes an LCD display that provides for easy programming and a flash memory to save programmed data. The Automatic Phone-Out Freeze Monitor is FCC approved and features a battery power backup feature (9-volt battery - not included). One-year limited warranty.