The cell phone signal jammer is an instrument used to protect the cell phone from receiving signals. The cell phone signal jammer broadcasts the same frequency signal to the GSM modem. Jamming is considered successful if the cell phone signal is disabled with the cell phone jammer enabled.
Cellular phones are full-duplex devices that use two frequencies simultaneously. One speaks and one listens. Signals are processed simultaneously. Some jammers can only block one frequency at a time, which causes both to be blocked because the phone thinks there is no service in the area because it only gets one frequency.
The principle of interrupting a cell phone is similar to how 3g interferes with other types of radio communications, in order to use a cell phone, a signal is sent from the cell phone to a cell tower. A city has several cell towers. As cell phone users move around an area, the signal is processed from tower to tower.
The cell phone jammer transmits on the same radio frequency as the cell phone, and it interrupts communication between the cell phone and the base station in the tower. Jamming is also known as a denial of service attack because it denies radio signals to users within the coverage area of the jamming device.
There are different types of cell phone jammers on the market today. Some devices can only block one frequency, while others can block multiple types of networks at the same time. The latter model can automatically switch from different networks to find open signals. High-end devices can block all frequencies at once, while others can tune to specific frequencies.
In short, they emit random static or noise over a wide range of frequencies, strong enough to keep an approaching device from connecting to the connection it should. Kind of like opening the hood next to a sports car engine while trying to talk to someone on the phone. There is too much local noise for the device to make regular connections. By quickly covering a range of frequencies, they can effectively prevent equipment from functioning properly.
The carrier frequency of the electromagnetic interference signal it transmits is the same as the carrier frequency, so the receiver and the amplifier are demodulated (reduced), the interference signal and the interference signal at the same time at the receiving terminal. It's like a fake (like jammer) transporter and a real jammer for the transporter, same look only the car receives from the cargo, the result is really fakes to the shipper together. The power of electronic interference is strong enough, limited by the interference signal, to achieve interference.