Mobile Phone Jammer is a device which blocks cell phone signals at that place where mobile phones are prohibited. This cell phone jammer is used to protect mobile phone signals from the base stations. this kind of devices are mostly used in offices conference hall, schools, Borders, movie theater, malls and many other places where mobile phones are not allowed. First Question is arising in mind how it works. This device works to block mobile phones signals from base station or in other words we can say that this device block transmission of signals to mobile phones.