Deluxe Freeze Alarms (model FA-D2) will dial out to three phone numbers when the temperature gets out of range, if the power goes out (immediate or 45 minute delay), or if the back-up battery needs replacing. The NEW FA-D2 now includes the ability to leave a number on a numeric pager and has a standby switch to disable the freeze alarm while you are in residence. Additional features include the ability to switch a relay by telephone, making this perfect for switching between two different thermostats, one set for high and one set for low - effectively being able to heat up or cool down a home before you arrive. Also includes a normally open auxiliary alarm input for hook up of other alarms, such as a water alarm, a motion sensor or a door open sensor. Anything that closes the contact will activate the auxiliary alarm, call out to your phone list and then play a custom recorded message related directly to the activated alarm device. Units include a transformer for a standard wall outlet and require a 9 volt alkaline battery for back-up power. Units will only work on an existing, standard, single telephone line. This alarm can monitor both a temperature rise and fall simultaneously with a temperature range of -45° F to 199°F.