How does Cell Phone Jammer Work?

More and more number of people is using cell phones now a day. The number of cell phone users in the world is increasing rapidly. People feel connected by having cell phone with them and they feel being cut off with the world without cell phone. Cell phones are being almost ubiquitous. Because of this ubiquitousness of cell phones, they are causing many problems in society. Some people don’t know when to talk, when to put mobile on silent mode or when to switch off mobile. These people cause disturbance in society. You would hate those people, who are spoiling your movie by talking loudly on cell phones in theatre. Some people talk in hospitals and some in church and temple. To avoid these kinds of disturbances, cellular jammers are used at these places.

You would be surprised to know that cell phone jammers were used in Indian parliament to avoid disturbances caused by ‘ring tone’ of members and to prevent leakage of fresh information caused by journalists during the session. Journalists used to send SMS about the discussions in the parliament. To avoid this, cell phone jammers were used in Indian Parliament.

After knowing these facts one would wonder, what is a cell phone jammer and how does it work?

What is cell phone jammer?

Technically speaking, a cell phone jammer is a device used to block cell phones from receiving signals from base stations.

How does Cell phone jammer work?

To know the working of cell phone jammer you should know how does cell phone work? Briefly speaking, a cell phone works by sending and receiving signals to the mobile tower and from the mobile tower. These signals contain information. The cell phone jammer works on the concept of blocking cell phone to communicate with tower. Thus jammer prevents cell phones from receiving or establishing any call.

Cell phone jammers transmit the signals on the same frequency which mobile phones use. This way jammers create disturbance for mobile phones. Mobile phone is a full duplex device that means it uses different frequencies for listening and talking. Jammers block any one of these frequency by transmitting relatively high power signals (noise) on the same frequency. Because of this high power, a cell phone can’t identify the signal from tower and it keeps searching for signals. So one can see ‘no signal’ or ‘Searching for networks’ or ‘no service’ in mobile phone’s display.

There are two signals, one is cell phone to tower and another is tower to cell phone. Jammers generally try to disturb tower to cell phone signals because towers are placed at distance so signals coming from them has low power. So it is easy for jammers to disturb tower to cell phone signal.

Cell phone jammers generally consist of power supply, internal circuitry and antennas.

Basic block diagram of it is shown below

Power supply

There are mainly two types of power supply. One is battery and other is direct mains power. Small range jammers use batteries. These batteries look like a cell phone battery. While wide range jammers are generally fed up by mains power. But a disadvantage of it is jammer work till the electricity is present.

Internal Circuitry

The most basic circuits are used in jammers. One part of its circuit is a voltage controlled oscillator. Voltage controlled oscillator is a circuit which generates a signal of desired frequency. Another part along with it is a tuning circuit which allows to change the frequency. After that a random noise is inserted into the signal so that mobile phone can’t identify the signal. Next stage is amplifier which increases power of the signal. And last stage is antenna.

Antenna

Antenna is a device which transmits the signal. Generally there can be three or more than three antennas in a jammer. Each one is for specific use like GSM, 3G, DCS, Wi-Fi etc.

Here are some images of jammers

Cell phone jammers are available in a few meters to several kilometers range depending upon its application.

There some countries where the use of cell phone jammer is allowed (legal). And in other countries it is not allowed (illegal) or one must have a license to use it.