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Multiple Frequency Disruptors

Multiple Frequency Disruptors (MFD) are one of the latest technologies for tactical teams. These frequency disruptors may be used in a diverse range of scenarios including hostage and barricade incidents, undercover narcotic operations, correctional contraband maintenance, terrorism prevention and more.

Frequency disruptors were developed several years ago by the military to interrupt enemy communications and acts of terrorism. An ever-increasing threat of terrorism is a “frequency-enabled” detonation of an explosive device. Terrorists are capable of wiring a wireless device, such as a cellular phone, to the detonator. When the wireless device receives an incoming frequency signal (incoming phone call) it triggers the detonator, setting off the explosion.

Frequency disruptors can provide several advantages to crisis negotiation and tactical teams during a hostage, barricade or suicide situation. The ability to control communications is a critical factor in the safe and successful resolution.

Traditionally, when responding to a residential hostage/barricade situation, CNT and SWAT teams were able to establish control over communications by working directly with the landline telephone service provider or by simply disconnecting the residence’s landline telephone connection. However, as the replacement of cell phone use continues to surpass the use of traditional landlines, this method of establishing communications control is becoming much less feasible.

For example, if a barricaded subject has access to a cell phone, negotiations are much more difficult. These barricaded subjects can freely make and receive phone calls to and from undesirable third parties such as the media, family or others who ultimately complicate or prolong the negotiation process.

Furthermore, barricaded subjects with cell phone access are much less likely to communicate on a throw phone from the police. The throw phone, of course, provides a secure line of communication as well as providing tactical teams with access to covert intelligence to improve the tactical decision-making process.

Undercover narcotic teams can now be equipped with frequency disruptors to prevent the raided subject from contacting other drug dealers during a raid. Several correctional facilities are now equipping themselves with frequency disruptors to prevent inmates from utilizing contraband wireless frequency devices like cell phones and pagers within the facility to communicate illegal activities with the outside.

How It Works

To understand how a frequency disruptor works, let’s consider some of the many devices that utilize wireless radio frequency (RF). For example, cell phones, radios, pagers, cordless phones, garage door openers and GPS receivers use radio frequency waves to operate.

Any wireless RF device can be compared to a handheld two-way radio. A two-way radio uses radio frequency waves to wireless transmit and receive data. The bandwidth on which a wireless device sends and receives data is limited to a specific range or size. When a frequency’s bandwidth becomes overloaded, for whatever reason, it is no longer capable of transmitting any additional data.

A frequency disruptor is programmed to operate on the same frequencies that common everyday wireless RF devices (cell phones, pagers, etc.) operate on. When a frequency disruptor is activated, the frequency bandwidth on which these common wireless RF devices operate becomes overloaded or flooded with data. When this occurs, there is no more room on frequency bandwidth to allow the common wireless to send and receive data over, thus disrupting the radio frequency transmission “path” between the devices.

In consideration of several wireless RF devices, when a frequency disruptor is activated, a cell phone, for instance, will typically 1) display a No Signal message, 2) display a No Service message, or 3) attempt to make the call, but the call will not connect. Furthermore, calls that are already in progress will also become temporarily disrupted.

You can also consider a tactical team assigned the task of serving a high-risk warrant on a location. If that location utilizes outdoor cameras for perimeter security, the deployment of a frequency disruptor should interfere with the RF video signals and render their surveillance system inoperable.

The frequency disruptors do not leave a signature to anger the subject. The subject knows only that his wireless RF device is temporarily not functioning. As far as the subject is aware, he only thinks that he is in a “dead spot” or his device is simply not functioning properly, common enough occurrences that do not raise suspicion.

Many Frequencies & Networks

How successfully a frequency disruptor can perform is dependent on several factors including the device’s inherent design. Some of the most important frequency disruptor design characteristics are the power disruption output (in watts), transmission type (frequency bands affected), and range. Wireless devices, such as cell phones, can operate on a wide variety of these networks and frequency bands!

For example, the transmission type that a cell phone uses is dependent upon the wireless network service provider. Wireless network service providers include Verizon, Cingular/AT&T, Sprint-Nextel and T-Mobile. All wireless network service providers utilize TDMA (time division multiple access) for transmission of digital data.

TDMA is a technology used in wireless communication devices that divides each channel into three time slots in order to increase the amount of data that can be carried. Digital-American Mobile Phone Service (D-AMPS), Global System for Mobile communications (GSM) and Personal Digital Cellular (PDC) use TDMA. However, each wireless network service provider implements TDMA in a somewhat different and incompatible way. TDMA operates at 850 MHz and 1900 MHz frequency bands.

An alternative is CDMA (code division multiple access), a second and third generation system that takes the entire allocated frequency range for a given service and multiplexes information for all users across the spectrum range at the same time. CDMA employs analog-to-digital conversion in combination with spread spectrum technology. This system operates at 800 MHz and 1900 MHz.

GSM is a variation of TDMA and is the most widely used of the three digital wireless technologies, i.e., TDMA, CDMA and GSM. This system operates at 900 MHz and 1800 MHz.

Verizon makes cell phones with and without 800 MHz AMPS. Sprint makes cell phones with and without 800 MHz CDMA. AT&T sells 900 MHz GSM-only phones, GSM & 800 MHz TDMA phones, and SGM-TDMA-AMPS phones. Likewise, Cingular sells SGM-only and SGM-TDMA-AMPS phones. T-Mobile uses 800 MHz GMS. Sprint- Nextel uses 800 MHz iDEN, formerly Motorola Integrated Radio System, MIRS.

Depending on the model, and there are a couple dozen, the BlackBerry cell phone operates on 800/1900 MHz CDMA or on 900/1900 MHz GSM. Tri-band BlackBerry phones use 800/1800/1900 GSM and 900/1800/1900 GSM. Of course, at least one quad-band version operates on all four frequency bands. Some BlackBerry phones also provide Nextel capabilities.

Selecting Equipment

When considering cellular applications, the frequency disruption will most likely be programmed to operate on one of the many frequencies used by cellular devices such as 800 MHz, 900 MHz, 1800 MHz and 1900 MHz.

When selecting a frequency disruptor device, it is important to make sure that device’s disruption output has been designed to disrupt several different transmission types used by wireless network service providers. If the device only disrupts a limited number of transmission types, the device may not perform as expected on the street.

For instance, if a frequency disruptor is procured that is intended to disrupt only CDMA (800 and 900 MHz) transmission, it will most likely only disrupt Verizon and Sprint cell phone users because these wireless service providers currently operate on CDMA.

To better ensure the best performance, it is strongly encouraged that the frequency disruptor disrupts CDMA, TDMA and GSM transmission. In addition to disrupting Verizon and Sprint phones, these types of frequency disruptors can also disrupt Cingular/AT&T, Motorola/Nextel and T-Mobile.

Directional or Not?

Another performance issue involves the direction in which the disruption output is radiated. A frequency disruptor’s disruption output can be directed in several different ways including: omni-directional (radial), semi-directional or beam defined. Each depends upon use of a particular antennae set. Frequency disruptors with antennae that are omni-directional will transmit the disruption output within a circle around the device. Depending on the design of the frequency disruptor, this output radius can range anywhere from 5 to 100 feet.

A semi-directional frequency disruptor’s disruption output is transmitted at a certain angle as a vector or V-formation away from the device. Since a semi-directional frequency disruptor’s output is more focused, it can typically achieve a greater effective operating range.

Some semi-directional frequency disruptors can achieve an effective operating range of 700 feet or more. Some frequency disruptor providers also have disruption output repeating devices.

Beam-defined frequency disruptors utilize antennae that the operator can manipulate to adjust the disruption output’s angle. Though beam-defined frequency disruptors can help focus the disruption output toward a target, they are by no means fully directional. In theory, a fully directional frequency disruptor would be defined as a device that can direct its disruption output specifically at a specific target without disrupting the frequencies of other wireless devices located in the vicinity of the target.

The ability to specifically transmit the disruption output to a specific target of interest does not yet exist. Regardless of the frequency disruptor’s output direction, all of these devices can utilize additional antennae and receivers that can be set up around a perimeter to repeat the disruption output to cover a desired area.

Three Different Disruptors

The ETGI Low-Level Frequency Disruptor has a disruption range of 45 feet with an output of 100 milliwatts. This unit is omni-directional, i.e., any device within a 45-foot radius of the disruptor can be affected. This is a small, hand-held disruptor. The best uses for this device are undercover and narcotics, typically to prevent a call-in.

Importantly, NOT all frequencies are disrupted by the Low-Level unit. CDMA/TDMA and AMPS in the 800 MHz range are disrupted, as are W-CDMA WLL and PCS/TACS in the 1900 MHz range. Critically, the GSM-type frequencies (900 MHz range) used by Cingular, for example, are not affected.

The ETGI Mid-Level Frequency Disruptor is a better choice for SWAT and CNT teams. This omni-directional unit has an output of 3.2 watts and has a range of 82 feet, i.e., 82 feet in any and all directions of the disruptor. The Mid-Level unit is about the size of a throw phone, so it is very portable.

Significantly, in addition to the 800 MHz and 1900 MHz ranges covered by the Low-Level unit, the Mid-Level unit also disrupts GSM in the 900 MHz range and DCS and DETC in the 1800 MHz range. Cingular uses a GSM-type frequency. Nextel uses an 800 MHz, iDEN frequency.

The ETGI High-Powered Frequency Disruptor is a semi-directional unit with an output of 16 watts and a (flat beam) range of up to 700 feet. The semi-directional device produces a 135-degree wide beam. The High-Powered unit is portable, but must be erected to be used. The High-Powered unit features an external battery pack or it can be operated by connecting the unit into an A/C power supply (wall outlet). In use, this disruptor is 8 feet tall. The High-Power unit disrupts the same type and frequency ranges as the Mid-Level unit.


Frequency disruptors certainly do have disadvantages and limitations. Like other wireless RF devices, they need to be connected to a power supply be it an internal or external battery, or a wall outlet. During prolonged use, battery-operated frequency disruptors’ voltage will become depleted under heavy use. As the battery power goes down, so does the disrupted range. Just like any battery-operated device, it is important to deploy with fresh, fully charged batteries. This point becomes ever more important should a frequency disruptor be deployed in an environment that doesn’t have any A/C power readily available, like in a rural setting.

Frequency disruptors differ in design, i.e., power output equals performance. Do you want to reach 40 feet, 80 feet or 150 feet? It makes a huge difference in power output. With the Mid-Level disruptor, for example, the SWAT operator must get the device within 80 feet of the subject.

Multi-story buildings pose an additional challenge. Will the 80-foot radius bubble reach the subject? The negotiator must know the subject may simply be able to move to a different part of the house, out of the range of the disruptor. The determined SWAT teams place two frequency disruptors on opposite corners of the dwelling.

Frequency disruptors are hampered by the same limitations as cell phones. Known as passive cell disruptors, steel girders and concrete may reduce the effectiveness of the disruptor.

All of the emergency responders need to know the frequency disruptor shuts down everything inside the radius. Other law enforcement units need to know a disruptor is in use. Anything wireless may be disrupted. Certainly, anything in the 800/900/1800/1900 MHz range will be.

The frequency disruptor output will flood several different types of frequencies, which may include the radio frequencies on which an agency’s first response team operates. For instance, some frequency disruptors can be turned on or off only manually. Since the device can be only manually activated, the tactical team must turn on the device before retreating to its cover. If the device disrupts the team’s radio frequency, it will be unable to communicate with its radios until it is out of the device’s disruption range.

To provide a solution for this issue, some frequency disruptor providers offer a cable and switch that can be used to turn the device on and off from a remote location. Before implementing any type of frequency disruptor device, agencies in a real-life situation should know what frequencies their teams operate on. The teams should thoroughly train with the device to minimize the risk of undesired disruption or interference with their radios as well as other wireless devices.

The other ETGI wireless negotiation devices, such as their line of high end and low end throw phones and the wireless Face-To-Face system, operate at frequencies other than those being disrupted by their Multiple Frequency Disruptor. However, it is still “possible” that a disruption will occur with their or other makes of gear. Check all of the wireless communication gear ahead of time!

Published in Tactical Response, May/Jun 2006

Rating : 9.5

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