Terrorists have long used cellular phones to trigger improvised explosive devices (IEDs) in their attacks throughout the world. Although the time lapse between the activation of the cell-phone trigger and the explosion detonation has been only seconds in some bombings, one London terrorist bomb took nearly an hour to detonate after the initial attacks. This extended time lapse between triggering and detonation indicates that cell-phone signal jamming equipment could be used to prevent cell-phone detonation of explosives. A jamming device blocks the cellular downlink frequencies, preventing a cell phone's ability to receive an incoming call (uplink capabilities still function); however, it cannot prevent a cell phone's alarm function from detonating a bomb. One expert estimates that jamming equipment can obstruct half of all cell-phone bombs, along with remotely controlled bombs that use other remote instruments, such as garage door openers or toys. Separate equipment exists that can prevent bombs that use the cell-phone alarm function. U.S. Federal law currently allows only Federal law enforcement agents to use such jamming equipment. Because of delayed Federal response to bomb discoveries at the local level, many local police agencies favor being allowed to purchase and use jamming equipment. The Cellular Telecommunications & Internet Association is currently working with the U.S. Department of Homeland Security to develop a protocol that will retain Federal authority for determining when and how jamming equipment will be used, while allowing for a Federal directive that allows a specific use of jamming equipment by local police.