Cell Phone Detectors and Jammers
By Ike Mowete ( mowete@hotmail.com )
Monday, August 30, 2004

A few days before the visit in November, 2003, of the
United States President, George Bush, to the United
Kingdom, the British press speculated to no end about the extraordinary security measures that would be taken to protect the visiting president against possible terrorist attacks. In addition to fretting about such routine measures as street closures and associated traffic jams, the press also indulged in speculating about the possibility of blocking cell phone signals along the routes to be taken by President Bush during his visit. This apparently innocuous speculation was no figment of the imagination of the English press because terrorists have been known before then, to have utilised cell phone signals for the remote detonation of bombs and explosives.

One often cited example in that connection is the near-successful attempt by Palestinian militants in May 2002, to cause a major explosion in Tel Aviv by placing an explosive wired to a cell phone in a fuel truck destined for Israel’s largest fuel depot. Although the attack was not successful to the extent that the fire that resulted from the explosion was quickly put out, that event revealed an important possibility of cell phone use in terrorist acts. And it is not surprising therefore that the pioneers (Ben Te’eni and Gil Israeli, co-founders of Netline Communications Technologies) in the design of devices that can block the operations of cell phones, had backgrounds in Israeli military intelligence. Their company’s first cell phone jamming product is a device that is designed to prevent cell phone communications in selected areas of a building or open space.

According to the partners, their activities in the design of cell phone detectors and jammers began when they realised that there was a market for counter espionage associated with the use of cell phones, after some slight modifications, as ‘bugging’ devices. A business operator, espionage operator, could conveniently ‘forget’ this suitably modified cell phone in the boardroom of a target company. This ‘innocuous looking, ubiquitous object’, could then be called from anywhere in the world, (without giving a ringing tone and with its screen remaining blank) to enable the intruder listen to an otherwise confidential conversation. However, because cell phones are obliged to periodically register with the network, for location update purposes, by transmitting signals at pre-arranged intervals to the serving base station, a cellular activity analyser can detect cell phone activity, even when the mobile station is in the idle mode. One particular brand of’cell phone detector (the cell phone detector plus) has the capability of detecting two-way radio and mobile communications in the continuous frequency range extending from 400MHz to 2GHz. This detector, whose picture is displayed in the illustration below, can be moved around or mounted on the wall, and under optimum conditions, has a range of between 2 meters and 30 meters, for all major communications standards.

Cell phone jammers are regarded as cheap and ready weapons in the fight against kidnappers and extortionists who, in some countries, operate with cell phones located inside prisons and jails.
In addition to such security reasons as those described earlier, a number of compelling reasons have been advanced to support arguments in favour of using cell phone detectors and jammers. For example, it is well-known that many cell phone users lack the courtesy to switch off their handsets in public places and places of worship. Mobile units consequently disturb such social functions as weddings, films, worship sessions in churches and mosques and lectures, when they ring up loudly. Cell phone jammers are designed to eliminate these sources of disturbance and irritation by ensuring that the potentially offending mobile units do not operate where they may constitute a nuisance.

Jammer design depends on the knowledge of the portion of the electromagnetic spectrum over which the cell phones operate, as well as the power levels at which the cellular communications activities are carried on. With this knowledge, all a jammer has to do is transmit on those channels, using higher power levels, which jammer signal then harmfully interferes with the ability of the mobile station to communicate with the serving cell, base station and hence, the network. A typical jammer has an output power level in the neighbourhood of 20mW, which is far larger than the power levels utilised in most mobile telephony communications. Effective jamming range is between 10 meters and 25 meters, depending on cellular system type and location. When the jammer is switched on, the screen of the victim mobile station will simply indicate that it is not receiving any signal from the network (‘no network’), and the phone user will not even realise that the unit has been jammed.

With the exception of Israel, Japan, India, and few other countries, the use of cell phone jammers is illegal. Regulators in those countries insist that the use must remain illegal because the network operators paid for the licenses to operate the network and consequently, acquiring certain ‘property rights’ in the process. Jamming signals associated with their operations, they argue, translate to infringements on those rights, which the regulator is bound by the terms of the license to protect. Opponents of the use of the jammer further insist that jamming cell phones amounts to infringing on the individual rights of the users. As Travis Larson (said to be spokesman for the Cellular Industry Association) puts it, “you are not allowed to barricade the street in front of your house just because of ambulances”, thus supporting the view that jamming has the potential of blocking important emergency calls. Proponents of jamming on the other hand, insist that ‘phoning is not a right, but privilege; and in some places phoning is as repulsive as smoking’.

One respondent to a survey carried out in Australia on the subject maintains that whereas he is, as a matter of convenience, in support of the use of mobile jammers, when it came to returning emergency calls from his children, every other consideration becomes secondary. Many others subscribe to what appears to a compromise solution. This class of contributors to the debate suggest that laws may be reviewed to permit jamming in high risk areas such as fuel stations and aeroplane in-flight situations and that if technology advances enough, jamming could be permitted in limited and restricted areas including the premises of banks, restaurants, cinema houses, places of worship and certain other similar public places as may be desirable. In such cases, legal parameters for jammer use could be set, including a regulator permission requirement.

Meanwhile, the debate continues, but chances are that technology will advance to the point of producing jammers that are smart enough not to breach the property rights of network operators, while enabling those wishing to do so, to somehow jam cell phones in a manner permitted by the law.