23-06-2012, 11:18 AM
A seminar Report On Cell Phone Jammers
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INTRODUCTION
Cell phones are everywhere these days. According to the Cellular Telecommunications and Internet Association, almost 169 million people in the United States had cell-phone service in January 2004. And cell phones are even more ubiquitous in Europe.
JAMMING BASICS
Disrupting a cell phone is the same as jamming any other type of radio communication A cell phone works by communicating with its service network through a cell tower or base station. Cell towers divide a city into small areas, or cells. As a cell-phone user drives down the street, the signal is handed from tower to tower.
HOW IT WORKS
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.
Cell phones are full-duplex devices, which means they use two separate frequencies, one for talking and one for listening simultaneously. Some jammers block only one of the frequencies used by cell phones, which has the effect of blocking both. The phone is tricked into thinking there is no service because it can receive only one of the frequencies.
INSIDE A CELL-PHONE JAMMER
Electronically speaking, cell-phone jammers are very basic devices. The simplest just have an on/off switch and a light that indicates it's on. More complex devices have switches to activate jamming at different frequencies. Components of a jammer include:
Antenna:-
Every jamming device has an antenna to send the signal. Some are contained within an electrical cabinet. On stronger devices, antennas are external to provide longer range and may be tuned for individual frequencies.
Circuitry :-
The main electronic components of a jammer are:
• Voltage-controlled oscillator - Generates the radio signal that will interfere with the cell phone signal
WHERE ARE CELL-PHONE JAMMERS USED
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.
[attachment=25185]
INTRODUCTION
Cell phones are everywhere these days. According to the Cellular Telecommunications and Internet Association, almost 169 million people in the United States had cell-phone service in January 2004. And cell phones are even more ubiquitous in Europe.
JAMMING BASICS
Disrupting a cell phone is the same as jamming any other type of radio communication A cell phone works by communicating with its service network through a cell tower or base station. Cell towers divide a city into small areas, or cells. As a cell-phone user drives down the street, the signal is handed from tower to tower.
HOW IT WORKS
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.
Cell phones are full-duplex devices, which means they use two separate frequencies, one for talking and one for listening simultaneously. Some jammers block only one of the frequencies used by cell phones, which has the effect of blocking both. The phone is tricked into thinking there is no service because it can receive only one of the frequencies.
INSIDE A CELL-PHONE JAMMER
Electronically speaking, cell-phone jammers are very basic devices. The simplest just have an on/off switch and a light that indicates it's on. More complex devices have switches to activate jamming at different frequencies. Components of a jammer include:
Antenna:-
Every jamming device has an antenna to send the signal. Some are contained within an electrical cabinet. On stronger devices, antennas are external to provide longer range and may be tuned for individual frequencies.
Circuitry :-
The main electronic components of a jammer are:
• Voltage-controlled oscillator - Generates the radio signal that will interfere with the cell phone signal
WHERE ARE CELL-PHONE JAMMERS USED
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.