A cell phone jammer is a piece of equipment capable of blocking reception or transmission of cell phone signals. This is mostly done by creating some form of interference at the operating frequency ranges of cell phones, which results in no signal or significant loss of signal quality. Although cell phone jammers could be used practically anywhere, they are mainly used in areas where silence is expected or required.
It’s great to be able to call anyone at anytime. Unfortunately, restaurants, movie theaters, concerts, shopping malls and churches all suffer from the spread of cell phones because not all cell-phone users know when to stop talking. Who hasn’t seethed through one side of a conversation about an incredibly personal situation as the talker shares intimate details with his friend as well as everyone else in the area?
While most of us just grumble and move on, some people are actually going to extremes to retaliate. Cell phones are basically handheld two-way radios. And like any radio, the signal can be disrupted, or jammed.
A cell phone jammer consists of:
Voltage-controlled oscillator – Generates the radio signal that will interfere with the cell phone signal
Tuning circuit – Controls the frequency at which the jammer broadcasts its signal by sending a particular voltage to the oscillator
Noise generator – Produces random electronic output in a specified frequency range to jam the cell-phone network signal (part of the tuning circuit)
RF amplification (gain stage) – Boosts the power of the radio frequency output to high enough levels to jam a signal.
When a cell phone jammer is active, most cell phones show no network signal, and when the cell phone jammer is switched off, the cell phone becomes active. Cell phones use unique frequencies for talking and listening. Most cell phone jammers block either of the two frequencies, indirectly providing the effect of prevention of both. Cell phone jammers work on the same principles as that of jammers used in preventing radio communication. They either function by disrupting the cell-phone-to-base-station frequencies or base-station-to-cell-phone frequencies.
A jamming device transmits on the same radio frequencies as the cell phone, disrupting the communication between the phone and the cell-phone base station in the tower.
It’s a called a denial-of-service attack. The jammer denies service of the radio spectrum to the cell-phone users within range of the jamming device.
Apart from military and law enforcement applications, cell phone jamming is illegal in many countries, including the United States. U.S. law bans the sale or purchase of cell phone jammers, and has some of the strictest laws in the world regarding their usage. Some countries such as Mexico allow use of cell phone jammers in public areas such as hospitals. Different countries have different laws regarding the use of cell phone jammers.
Some cell-phone jammers are made to look like actual phones. Others are briefcase-sized or larger.
The biggest jammers used by police and the military can be mounted in vehicles for convoy security.