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About Cell Phone Signal Jammers

What does jammers? How to it working? This article will help you answer these questions.
Cell phone jamming devices overpower the cell phone by transmitting a signal on the same frequency and at a high enough power that the two signals collide and cancel each other out. Cell phones are designed to add power if they experience low-level interference, so the jammer must recognize and match the power increase from the phone.

Development history of mobile phone jammers


Cell phone jamming devices were originally developed for law enforcement and the military to interrupt communications by criminals and terrorists. The bombs that blew up commuter trains in Spain in March 2004, as well as blasts in Bali in October 2002 and Jakarta in August 2003, all relied on cell phones to trigger explosives. It has been widely reported that a cell-phone jammer thwarted an assassination attempt on Pakistani President Musharraf in December 2003. When President Bush visited London in November 2004, it was reported that British police considered using jammers to protect the president's motorcade through London.
During a hostage situation, police can control when and where a captor can make a phone call. Police can block phone calls during a drug raid so suspects can't communicate outside the area. Cell-phone jammers can be used in areas where radio transmissions are dangerous, (areas with a potentially explosive atmosphere), such as chemical storage facilities or grain elevators. The TRJ-89 jammer from Antenna System & Supplies Inc. carries its own electrical generator and can block cellular communications in a 5-mile (8-km) radius.
There are debates in many countries as to how schools should address the issue of mobile phones. Some advocate for a complete ban while others promote the use of mobile phones as a teaching tool in classrooms. This debate has most recently been seen with the Mayor of New York removing a 10-year ban of phones on school premises in March 2015, stating that abolition has the potential to reduce inequality (Sandoval et al, 2015).2 Despite the extensive use of mobile phones by students and the heated debate over how to treat them, the impact of mobile phones on high school student performance has not yet been academically studied. In this paper, we estimate the effect of schools banning mobile phones on student test scores.
When someone hears about cellphone jammers, you might have an initial overall negative impression. After all, why would someone want to cut off the communication of cell phone users? The reality is, there are really many reasons to consider using a cell phone signal jammer — and within a variety of settings.
We find that following a ban on phone use, student test scores improve by 6.41% of a standard deviation. Our results indicate that there are no significant gains in student performance if a ban is not widely complied with. Furthermore, this effect is driven by the most disadvantaged and underachieving pupils. Students in the lowest quartile of prior achievement gain 14.23% of a standard deviation, whilst, students in the top quartile are neither positively nor negatively affected by a phone ban. The results suggest that low-achieving students are more likely to be distracted by the presence of mobile phones, while high achievers can focus in the classroom regardless of the mobile phone policy. Schools could significantly reduce the education achievement gap by prohibiting mobile phone use in schools, and so by allowing phones in schools, New York may unintentionally increase the inequalities of outcomes. We include several robustness checks such as an event study, placebo bans, test for changes in student intake and range of alternative outcome measures.

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