In January, Perfectjammer said its researchers installed the jamming technology in a utility closet adjacent to a 13-by-eight foot cell on the ground floor of the prison’s housing unit, according to the study. It successfully blocked cellphone transmissions in commercial bands between 700 and 2170 MHz, but did not disrupt commercial transmissions when monitored at 20 feet and 100 feet outside the cell, said the study.
Cellphone GPS jammer is the App that allows you to detect presence of jamming devices around. In that situation your mobile phone loses the ability to make a phone call. If it happened, the App gives you a visual or sound message. The time for reaction on a working jammer depends on hardware communication part of your device and typically can be in 30-60 sec range.
At the measurement locations inside the prison cell, measured differences in incident power between when the cell phone jammer was on versus off showed that jammer incident power levels were much greater than that of the ambient CMRS power levels. For the outdoor locations where jamming was not intended, the jammer’s incident power was measurable at 100 feet from the building. However, outdoors the incident jammer power levels were lower than the ambient CMRS levels. This was because the jammer signal strength was lower outdoors than indoors, while the ambient CMRS signals were stronger outdoors than indoors.
As far as I know, there is none. A jammer transmits radio waves under same frequency of a cell phone which intervenes connection between a mobile and the tower. A normal mobile will not have such unit fabricated in their motherboard. A separate signal jammer is what you should buy to achieve this.
The fact that Burail jail has a cell phone jammer with 2G reception only made it easy for inmate Rajan Bhatti to use mobile phones having 4G network, as its signals cannot be jammed by the Burail jail jammer. An official of the Burail jail admitted that the 2G network jammer at the jail was of no use. “The jammer does not hamper the usage of 4G mobile phones which are in every hand nowdays and 4G SIMs are easily available,” said the official.