Alarm Clock Radios, Atomic Alarm Clocks & Travel Alarm Clocks

Alarm Clock:  Of course, an alarm clock is a clock that you typically use to get you up in the morning.  But there are many other considerations, please see below.

Travel Alarm Clock:  Travel alarm clocks are alarm clocks that are particularly designed to take with when you travel.  They are generally designed to be small and light, and generally, but not always run on batteries.  The smallest generally use watch batteries for power.  This makes the clock smaller and lighter, but the batteries can be a little tougher to find, especially on the road.  A few also have low power flashlights built in, which comes in handy for finding your way around in the middle of the night in a strange room.

Projection Alarm Clock:  Projection alarm clocks actually project the time on the ceiling over the bed, or onto a wall.  Typically, the ones that come with a plug-in power supply can project continuously, the less expensive ones that do not only project when you push a button. The strong point of these clocks, at least the continuous projectors,  is that when the room is dark, you can just look up and see the time.  You don't need to find the clock and possibly push a button to illuminate the display.  Some clock models can also project either indoor or outdoor temperature. 

Quartz alarm clock:  Quartz alarm clocks, like any quartz clock, has it's accuracy controlled by a quartz crystal.  A precisely trimmed quartz crystal is used to generate an electrical timing signal that regulates the speed of the clock.  Quartz clocks may gain or lose around one second per day, and the drift rate may depend somewhat upon temperature.

Auto setting alarm clock:  Auto-setting alarm clocks are a relatively new technology.  They are available under a number of names, depending on the manufacturer.  Auto-setting clocks are built with a quartz crystal to regulate speed, and a built in integrated circuit that knows the approximate time, and the date.  Although they can gain or lose time like any quartz clock, they have one advantage.  They know about, and will automatically adjust for  daylight savings time.

Atomic clock, or Radio Controlled clock:  The United States Government National Institute of Standards and Technology  maintains a radio station, WWVB, in Ft. Collins, Colorado.  This radio station transmits highly accurate time information.  Atomic, or Radio Controlled clocks receive this signal when they can, and set themselves.  These will maintain time accurate to a fraction of a second as long as they are placed in a location where they can receive the signal.  Like any radio receiver however, they may not be able to receive the signal if they are in a building with a lot of steel in the structure, near computers or cordless phones that may generate interference, or if the weather is unsuitable.  Please note.  The signal they receive does not propagate well during the day.  That's the nature of the signal, not the clock.  These clocks are designed to catch the signal when they can, generally in the middle of the night, calibrate themselves, and then run quite accurately for days until they can catch another signal.  When you first put in the batteries, they will most likely not set themselves until the middle of the night.  The analog clocks generally tick for a few seconds, advance to 4:00, and wait.  The digitals display various things while they wait.  That's normal.  By morning, weather permitting, it should be correct.