Casio F91W
From Wikipedia, the free encyclopedia
The Casio F91W is an inexpensive quartz digital watch, manufactured by the Japanese firm Casio Computer Co., Ltd.. It was introduced in 1991. This watch is widely available throughout the world in various packaging.
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[edit] Specifications
The F91W has a 1/100 second stopwatch with a capacity of up to 59' 59.99" and measuring modes of net time, split time, and 1st-2nd place times. There are the options of an hourly time "beep" and a daily alarm. It has an automatic calendar, although auto-adjustment for leap-years is not supported as the watch does not record the year.
The manufacturers say the watch is accurate to ±30 seconds per month. It uses a CR2016 lithium battery, with a claimed battery life of approximately seven years (assuming 20 seconds of alarm and 1 second of light usage per day). The watch case measures 37.5 x 33.5 x 9.5 mm and weighs 20 g. The manufacturer's module number for this model (stamped on the stainless steel rear of the watch case) is 593. The watch front is marked 'WATER RESIST', but this means 'splashproof' only, and it cannot be used when showering or swimming/snorkeling.
Since the watch was introduced in 1991 it has only been updated once. The change was to the backlight (for example Casio A-168W) which went from the standard light in older watches to the blue-green electro-luminescent backlight seen in many of today's watches.
[edit] Operation
The watch is controlled by three side push-buttons. The upper left button turns on the backlight, cancels the alarm, and is used for selecting settings. The lower left button cycles the modes of the watch: → Alarm → Stopwatch → Time adjustment and back to the normal time display. The button on the right is the function button: when used after pressing the lower left mode button it starts and stops the stopwatch, or changes the settings currently being adjusted; but when pressed alone switches between the 12 and 24 hour modes.
The time or date is adjusted by pressing the lower left button three times to bring the watch to time adjustment mode. This causes the seconds to flash on the display. The top left button is pressed to cycle through seconds, hours, minutes, month, date, day, and normal mode. The right button is then pressed to adjust the flashing value displayed. When the adjustments are finished, the bottom left button is pressed repeatedly until the watch returns to normal mode.
The watch's display shows the day of the week, day of the month, hour, minute, seconds, and the signs for PM (or 24-hour clock), alarm signal, and hourly signal (double beep on the hour).
In stopwatch mode, minutes, seconds and hundredths of a second are shown.
[edit] Claimed use in terrorism
United States intelligence officials have identified the F91W as a watch that terrorists use when constructing time bombs.[1][2][3][4] This association was highlighted in the Denbeaux study, and may have been used in some cases at the Guantanamo Bay detention camp.[5] An article published in the Washington Post in 1996 reported that Abdul Hakim Murad, Wali Khan Amin Shah, and Ramzi Ahmed Yousef had developed techniques to use commonly available Casio digital watches to detonate time bombs.[6]
[edit] References
- ^ "USA v. al Qahtani" (PDF). US Department of Defense. November 7, 2005. http://www.defenselink.mil/news/Nov2005/d20051104qahtani.pdf. Retrieved on 2007-02-27.
- ^ "Why Am I in Cuba?", Mother Jones (magazine), July 12, 2006
- ^ Guantanamo Captives Jailed Because Of Digital Watches, WCVB, March 10, 2006
- ^ Summary of Evidence memo (.pdf) prepared for Sabri Mohammed Ebrahim Al Qurashi's Combatant Status Review Tribunal - October 13, 2004 - page 216
- ^ Empty Evidence (02/03/2006), National Journal
- ^ R. Jeffrey Smith (July 21, 1996). "New Devices May Foil Airline Security". Washington Post. pp. A01. http://www.washingtonpost.com/wp-srv/national/longterm/twa800/bomb.htm. Retrieved on 2008-03-14.
