Terrorists said to own a Casio F91 watch

The late Sayed al Shiri, formerly the number two in Al Qaeda in the Arabian Peninsula, is said to be wearing a Casio F91 in this image.

Osama bin Laden is said to be wearing a Casio F91.

It is widely reported that Terrorists own Casio F91 watches. Over five percent of the individuals held in extrajudicial detention had their ownership of a Casio watch used as one of the justifications for their indefinite detention without charge.

There is a grain of truth to the claim that the watch is used by terrorists. In December 1999 Ahmed Ressam, the "Millenium Bomber" was caught trying to cross from Canada to the United States, with copious bomb-making components. His kit includes multiple Casio F91 watches, as well as special custum built circuit boards, designed to allow the Casio to serve as the core timer in a time-bomb. What US intelligence spokesmen routinely fail to mention when they inflame the public's fear of terrorism is how crucial custom built circuit boards are when using the watch as a bomb component. The voltages used in the watch are puny, barely enough to make a tiny speaker chirp, and to make a tiny LED light up.

This sequence of photos shows a modified Casio F91, hooked up to a small box containing a custom-built amplifying circuit.

This sequence of photos shows a Casio F91 mounted on a custom-built amplifying circuit, necessary to step the power of the watch's timer.

A custom built circuit board is essential to step up the power and voltage of the watch's timer to an output that could trigger a blasting cap, or otherwise trigger an explosion.