The two-step process is intended to prevent accidental activation.

The fuze is covered by a safety cap that prevents accidental activation.

It is difficult to see how such a system can operate without some mechanism to prevent explosive activation.

On some computers, it is a pinhole into which a straightened paperclip - or syringe - must be inserted (to prevent accidental activation).

When the launch vehicle is no longer a threat, the range safety system is typically safed (shut down) to prevent inadvertent activation.

This is to prevent accidental activation when the unit gets wet from rain or shipped seas.

Its main function is the inhibition of the complement system to prevent spontaneous activation.

Several antagonistic drugs are used to block the action of allergic mediators, or to prevent activation of cells and degranulation processes.

So, Dr. Haas said, "I'm not sure we can ever prevent activation."

This behaviour allows users to decide themselves whether they want to use the key, or to disable it to prevent accidental activation.