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As it comes from the factory, the WT-2165U is set to automatically adjust for Daylight Saving Time changes in spring and fall. If you live in an area (Indiana or Arizona, for example) that does not observe DST, you can disable the DST change during clock setup. 

Each of the WT-2165U's two alarms consists of a series of beeps, at first intermittent pairs of beeps and later becoming more constant. Each alarm has its own distinctive tone and operates independently from the other alarm. When an alarm is sounding, you can activate the snooze function by pushing down on the top of the clock and rocking it backward. (It's a good idea to practice doing this after you set up the clock so that you'll know how to do it when you actually use the clock.)

You can set the duration of the clock's snooze function for 0 minutes to 59 minutes. If the setting is 0, the alarm will turn off for 24 hours. During the snooze period, the bottom line of the LCD panel shows a countdown (minutes and seconds) until the alarm will sound again. If you push any other button during a snooze period, the alarm is turned off for 24 hours. (We found that you actually have to hold the button depressed momentarily to stop the alarm from beeping.) Also, the electro-luminescent backlight turns on automatically for about 5 seconds when an alarm goes off or when you activate the snooze function. To turn on the backlight at any other time, push and rock the clock as if you were activating snooze, or momentarily press any button on the back of the clock.

When you go through the WT-2165U's setup process, you'll notice that the time zone is displayed as an hour offset from Greenwich Mean Time (GMT). The factory default is -5 hours, which is the U.S. Eastern time zone. When you're traveling, you'll need to change to the appropriate time zone. The clock will only search for a time signal when it is set for GMT -4 (Atlantic time) to GMT -10 (Hawaii time). However, you can set the time zone to any zone from GMT to GMT -12. Outside of these zones (for example, if you're in Hong Kong), you'll need to manually set the clock to local time.

By the way, we suspect that the WT-2165U may not always be able to receive the WWVB time signal in zones outside of GMT -5 (Eastern time) to GMT -8 (Pacific time). This is because 2000 miles (3200 km) is normally the maximum reception range for this kind of clock. However, WWVB has increased its signal power from what it was originally, so the clock's reception range may exceed 2000 miles in some instances.

The WT-2165U atomic travel alarm clock is good-looking and offers lots of useful features at a very reasonable price. We've tried it out, and we like it a lot. We think you will, too. 

Features:

• Sets automatically to WWVB radio signal (manual setting is also possible).
• Large (about 0.5 inch)12-hour or 24-hour time display (hour and minute).
• Dual alarm settings with an adjustable snooze function (0 to 59 minutes).
• Calendar/alarm display toggles via pushbutton between day/month/date, month/day/year, Alarm 1 time, Alarm 2 time, and seconds.
• Time zone setting (13 available, -1 to -12 hours or GMT), with map display for the 4 continental U.S. time zones (Eastern, Central, Mountain, and Pacific).
• Daylight Saving Time ON/OFF option.
• LCD panel has an electro-luminescent backlight with automatic turn-off.
• Powered by one AAA (1.5V) alkaline battery (not included), with normal life of about 1 year.

Specifications:

• Time source / frequency: WWVB / 60 kHz
• Power source: 1 x AAA (1.5V) alkaline (not included)
• Battery life: approximately 12 months
• Dimensions:
  2.63 inches (67 mm) wide
  3.5 inches (89 mm) high
  0.9 inch (23 mm) deep with front cover closed
  3.4 inches (87 mm) deep with front cover open to function as clock base

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 WT-2165U Radio Controlled Digital Travel Alarm Clock:

The La Crosse Technology Radio Controlled Digital Travel Alarm 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 battery, 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.