The 00990 Acu-Rite Wireless Indoor/Outdoor Thermometer Combo Pack with 2 Main Units that simultaneously display both the indoor temperature and, as received from the included remote sensor, the outdoor temperature. Maximum transmission range of the remote sensor is 100 feet. Both the main units and the remote sensor can be wall-mounted or free-standing. 

The 00990 Wireless Indoor Outdoor Thermometer main unit monitors and displays the indoor temperature plus the temperature in one outdoor or other remote location by means of the included thermo sensor. Unlike some temperature stations, the 00990 simultaneously displays the indoor and outdoor temperatures, so you don't have to actively select one or the other for viewing. Temperatures are displayed in °F only. Both the indoor and outdoor temperature digits are just over 1/2 inch tall, with tenths of a degree about half that size at 5/16 inch.

The remote temperature sensor that comes with the 00990 Wireless Thermometer Combo Package is white in color and extremely small in size. This is a non-displaying sensor that can either be wall-mounted or placed on a flat surface.

Operating (indoor) temperature range of the main unit is 32°F to 122°F. Operating temperature range of the included remote sensor is 0°F to +130°F. 

As mentioned above, both the main unit and the remote sensor can be wall-mounted (via keyhole slots on the back) or free-standing. The bases of both the main units and the remote act as stands. The remote has a water-resistant (splashproof) case, but for proper operation you must mount the remote where direct rainfall and direct sunlight cannot fall on it.

Batteries are not included with this product. You'll need 6 AAA (1.5V) alkaline cells--2 for each main unit and 2 for the included remote sensor. No display means that the batteries in the main unit need to be replaced. When the remote sensor needs new batteries (or if it is moved out of transmission range), three dashes (- - -) are continuously displayed in the outdoor temperature section of each main unit's display. You probably already know that alkaline batteries lose power and can actually freeze as temperatures fall to near 0°F and below. Now that AAA lithium batteries are available, you'll want to use them in the remote instead of alkaline batteries when temperatures are expected to remain significantly below freezing for an extended period of time.

Here's a tip: With this product, you need to install batteries in both main units before installing them in the remote sensor.

If you need a simple, compact, and inexpensive wireless thermometer that's really easy to set up and use and includes a second main unit for use in another indoor location, the Acu-Rite 00990 Wireless Indoor/Outdoor Thermometer Combo Pack is a great choice. Small enough to fit almost anywhere, this thermometer is perfect for any two rooms in the house--or for two office locations close to one another. This product comes with a 1-year factory warranty.

Specifications:

Main Units:

• Indoor temperature measuring range: 32°F to 122°F
• Temperature resolution: 0.1°F
• Power: two AAA (1.5V) alkaline batteries per main unit
• Dimensions:
  • Height: 3-3/4 inches (95 mm)
  • Width: 1-1/2 inches (38 mm)
  • Depth: 1-5/8 inches (41 mm)

Included Remote Sensor:

• Outdoor temperature measuring range: 0°F to +130°F
• Temperature resolution: 0.1°F
• RF transmission frequency: 433MHz
• RF transmission range: 100 feet (30 meters) maximum in open space with no interference
• Power: two AAA (1.5V) alkaline batteries (for use in sub-freezing temperatures, lithium batteries are recommended instead of alkaline)
• Dimensions:
  • Height: 2-1/2 inches (64 mm)
  • Width: 2-1/8 inches (54 mm)
  • Depth: 1-1/8 inch (29 mm)