La Crosse Technology WS8117UOAK Atomic Clock with Indoor and Outdoor Temperatures and Moon Phase, Oak Finish

The WS8117UOAK is medium-large in size (about 12 x 8 inches) and has large digital displays for great readability, even from a distance. Hours and minutes are displayed in extra- bold digits a full 2 inches tall. Temperatures are displayed in bold digits almost 3/4 inch tall; day and date, in digits about 1/2 inch tall. 

Displayed information in the initial display mode (pictured) includes time (hour and minutes), month and date, weekday, indoor temperature, outdoor temperature, and moon phase. Three other display modes let you display clock seconds digitally in place of the weekday, the indoor temperature, or the outdoor temperature.

Mount this clock on a wall, or extend the clock's integral foldout stand to use it as a freestanding unit on a table or shelf.

Features:

• Sets automatically to WWVB radio signal (manual setting is also possible).
• User-selectable 12- or 24-hour time display. Hour and minutes are separated by a flashing colon (:) that indicates seconds.
• Daily alarm setting with snooze function.
• Calendar display with weekday abbreviations in your choice of four languages: English, French, Spanish, or German.
• Time zone setting (13 available).
• Daylight saving time ON/OFF option.
• Moon phase (8 phase icons).
• Indoor temperature display.
• Outdoor temperature display via wireless remote transmitter.
• Temperature displays are user-selectable for either °F
  or °C.
• Clock can be wall mounted, or integral foldout stand can be extended for placement on a table or shelf.
• Clock is powered by two AA alkaline batteries (not included), with normal life of about 1 year.
• Outdoor temperature transmitter is powered by two AA alkaline batteries (not included), with normal life of about 1 year.

TX6U Outdoor Temperature Transmitter:

• Remote transmission of outdoor temperature to clock via 433 MHz signals.
• Wall mounting (remote unit snaps into its own wall-mounted bracket).

Specifications:

• Indoor temperature measuring range:
  32° to 122°F with 0.1°F resolution
  (0° to 50°C with 0.1°C resolution)
• Outdoor temperature measuring range:
  -21.8° to 157.2°F with 0.2°F resolution
  (-29.9° to 69.9°C with 0.1°C resolution)
• Temperature checking intervals:
  Indoor: every 10 seconds
  Outdoor: every 5 minutes
• Transmission distance:
  82 feet (25 meters) maximum
• Clock dimensions:
  12.20 inches (310 mm) wide
  8.03 inches (204 mm) high
  1.18 inches (30 mm) deep (excluding foldout stand for freestanding applications)
• Remote transmitter dimensions:
  1.57 inches (40 mm) wide
  5.04 inches (128 mm) high
  0.9 inch (23 mm) deep

The NIST (National Institute of Standards and Technology, Time and Frequency Division) maintains a radio station, WWVB, in Ft. Collins, Colorado. The WWVB radio station derives its signal from the NIST atomic clock in Boulder, Colorado. A team of atomic physicists is continually measuring every second of every day, to an accuracy of ten billionths of a second per day. These physicists have created an international standard, measuring a second as 9,192,631,770 vibrations of a Cesium-133 atom in a vacuum.

WWVB (the station’s identification just like any other radio station) continuously broadcasts time and frequency signals at 60 kHz. The carrier frequency provides a stable frequency reference traceable to the national standard. There are no voice announcements on the station, but a time code is synchronized with the 60 kHz carrier and is broadcast continuously at a rate of 1 bit per second using pulse width modulation. The time code contains the year, day of year, hour, minute, second, and flags that indicate the status of Daylight Saving Time, leap years, and leap seconds.

The La Crosse Technology WS8117U-O Digital Atomic Clock:

The La Crosse Technology Digital Atomic Clock maintains its incredible accuracy by automatically tuning into the WWVB radio signal. The built-in antenna ensures reliable signal reception up to 2000 miles (3200km) from the WWVB transmitter. As a result, the La Crosse Technology clock will calibrate to the atomic clock not only throughout the mainland U.S. but also in much of Canada. You need only insert the batteries, wait until the signal is received, and program the desired additional settings. In locations outside of WWVB range, the La Crosse clock can be manually set and will provide the high degree of accuracy of any quality quartz clock.

In a nutshell, here's how the the La Crosse clock works: The clock's antenna is specifically tuned for optimal reception of the 60 kHz time signal. The time signal received on the antenna is demodulated by an onboard receiver, which sends the information to the clock's CMOS microprocessor for decoding. Once your clock has automatically set its time for the first time, it ensures continuing accuracy by automatically tuning into the WWVB radio signal once per day at midnight. (If no signal is detected, the clock performs its WWVB check hourly until the signal is found.) As long as your clock is kept within transmitter range, it will continue to display the absolutely precise time, automatically adjusting for summer time/winter time changeovers if the daylight savings time option is ON. Should you move your clock out of transmitter range for an extended period of time, the clock will continue to operate as a highly accurate quartz-controlled clock. Upon re-entering the transmitter range, your clock will correct itself again to the precise WWVB time signal.