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By Robert Burchett; Certified Communications Engineer

Most everyone knows how a metal detector works by now; in simple terms, you walk between the bars, the magnetometers SEND some magnetic energy to objects on your person, the item disrupts the magnetic field, the detector senses this and alerts. This is the same for detectors from $100 to $10,000


Cell Phone Detectors work exactly the opposite; they LISTEN for the radio signals that come out of the phones. This is completely different and so it is helpful to explain how to deploy them and how they can be a major part of your security procedures to do the best possible job. When in doubt CALL first!


What they WILL detect upon:



What they WON’T detect upon:



How phones register on the network and how we use this fact to catch them.

Phones RANDOMLY send ‘pings’ of short information bursts to the cell network to let it know where they are, request if there are voicemail messages in queue, texts waiting for them, etc. Many of the detectors on the market will not detect these VERY short bursts (about 1/10 of a second) but we do. This is good and bad…here is why:


If you walk past the detector with your phone ON (as previously described) and the phone isn’t talking, texting or registering then the detector won’t hear it…this is because the phone has a very small battery and regardless of the fact that it is a cell phone, it won’t send radio signals until it needs to; if it did then the battery would go dead in an hour and that would not be useful to any of us.


So: when you place the detector inside of a secure area AND then when a concealed phone registers on the network we will let you know that it happened. That is a good thing; no metal detector can do this.


These bursts are not at any specific time; we see them from 2 to 5 times per hour; but no one really knows for sure…we just lie in wait for them to ping and then alert you accordingly which a metal detector cannot do as you have to be exactly between the bars in order to have them work…we must use each machine the correct way to get it to perform the job it was designed to do.


When is registration a blessing and a curse at the same time?

Cell phone text & voice calls transmitted signals are a “managed” signal for the most part; this means while you are moving toward a tower the system tells your phone to turn the power down. If you are moving away from it they say turn your power up. This makes your tiny battery last longer and we are all happier for it…but then comes the “curse” part. When a phone “loses sight” of the cell phone network then it is no longer a ‘managed’ signal and that can be ‘induced’ by storage in a locker or below ground for example where it can’t hear its network.


This means that WHEN it does transmit the registration burst (and this can be quite often) the power output will be at MAXIMUM the phone has capability of.  Blessing? Sure; that means we can catch them easily. Curse? Yes; that too; since cell phone signals transmit through walls…and everyone knows that.


When can an unmanged phone signal be a problem? Many facilities require that you put your phone in a locker at the front of the building and then the phone usually loses contact with the network. Should the phone be turned ON when in that locker some of them will begin a series of ‘cries for help’ or constant ‘registration’ bursting to try and acquire connectivity. This is an unmanaged call and typically at full power which can travel several floors or through many walls as it tries to connect; and a detector placed near it will alert on this signal constantly…this is NOT a “false” alert, the detector is simply doing its job and informing you of the event. Be aware & use it to your advantage; not as a problem or issue to be avoided.


Where else can this phenomenon occur?

Suppose a phone is taken below ground level or inside of any “shielded” environment where it is on the person, powered up and on “standby” but can’t connect with the network. Some phones have been observed to constantly attempt to ping the network with repetitive registration bursts over and over trying to contact the system to no avail.


Properly placed and monitored detectors will alert on this and inform you immediately despite the fact that no OUTSIDE signal can get in…and that means the detector is doing a great job of alerting you to the event. These phones are subject to their internal programing by their manufacturer; so we see some that DO register with zero signals and some that do NOT. Facility managers ask why the detector has been known to alert in “radio dark” areas and this is why. Sometimes the phones are designed to NOT do anything when there is no network as well.


Consider that our very expensive ($5000+) metal detectors can’t do this at all no matter the threat level unless you specifically walk between the bars, the fact that our highly engineered cell phone detectors WILL alert you to phones in unauthorized areas can be a major component to your security policy…if properly deployed.


Where to properly place the detectors for maximum effect is very important; pay close attention here to get the most out of your security detection system with the maximum policy enforcement:

You can install them at the door, in front of the entrance to the secure area BUT be aware that nearby (lobby, street, etc.) locations where phones are permitted to be used and these radio signals pass through walls…we expect and demand that they do…so this is no surprise. We just need to take it into account. Detectors placed there become Behavior Modifiers which is GOOD.


If you want the HIGH DETERRENT factor that our detectors are well known for then by all means place one AT the entrance but be sure to turn it down LOW on sensitivity so it doesn’t just alert all day long…after a while the personnel nearby will become quite annoyed with it and either unplug it or simply ignore it completely…even if it is telling you exactly what you wanted to know. This is the correct way to implement an effective security policy. Get every bit of the deterrent factor you can and then catch the ones that were missed by placing detectors INSIDE of the secure area. This will maximize the investment AND modify their behavior as well.


Suppose you have a secure area/ part of a building/ room/ floor where phones are NOT allowed and it is below, above or adjacent to a NON-secure area where phones ARE permitted to be used (cafeteria, smoke area, restroom, hall, etc.). This creates manageable issues and must be taken into account.


The way to deal with this is to put the detector as FAR away from the non-secure area (don’t forget the floor above and below too!) and adjust the detector low enough to try and not hear outside of the protected area while hearing the inside…this is a little difficult and here is why:


How far away will they detect phones? There is no ‘finite and specific’ distance that phones will be detected. This is due to the variable power output discussed previously. There are 9 steps of power up/ down that a phone will send out when under control of the network so no one knows what power setting the phones are allowed to send at PLUS:


There are several FORMATS of cell phone signals and in order of the most-to-least power being transmitted they are as follows:


  1. IDEN (aka: Nextel) has the most power of any digital phone signal currently
  2. GSM (AT&T, T-Mobile, etc.) has the next highest power-per-bit quantity
  3. CDMA (Sprint, Verizon, etc.) also known as “spread spectrum” has a lower power per bit
  4. LTE/ HSPA and other 4th generation (4-G) types of ultra-wide-bandwidth transmissions


This means that the detectors will alert on a GSM phone when it is farther away than for example a CDMA phone if both are “unmanaged” (at maximum power) or “managed” (variable power but probably lower than full) at the moment of transmission. That makes it difficult to measure exactly where the pickup zones are, how far away we can ‘hear’ it and alert the incident to you. This is why there is no “default” or “factory setting” for sensitivity.


Handheld detectors; what they do and don’t do:

Handheld detectors are great for certain specific applications; and, like everything, they have capabilities we employ but need to understand them to get the most from their ability. (We don’t call it “limitations”).


The good parts:


The bad parts:


Get the most out of your security system:




Handheld detectors come in different form-factors and pickup/ alert methods. Remember their capabilities and see the differences in the units shown as follows:

Wideband Unit

Wideband Unit: One type of ULTRA-WIDE-BAND RF DETECTOR that is quite popular is the Wideband Detector shown. This unit picks up cameras, bugs, surveillance mikes, GPS trackers etc. that use CELLULAR to transmit out

Class-Act Classroom
Pocket Version

The Class Act ( pocket detector is designed for covert use like in the classroom where instructors want to be alerted to student’s improper use of phones. This unit is very small and alerts the wearer to the detection event by silently vibrating.


This unit is “OFFICE FRIENDLY” and wall mounts or sits on the desk in your conference/ board room environment. Comes with AC power and alkaline battery operation for portable use or where no power outlet is available. 



Model 810 on Standby  





This model comes with the flashing sign stating “Cell Phones Are NOT Allowed In This Area” which informs the hearing-impaired (for ADA compliance) and also is good for quiet environments like churches, libraries, military conferences, etc. Choose this type when placing it at the ENTRANCE to a secure facility for overt policy enforcement alerting. The obvious nature of it helps your security policy to succeed with the intended Behavior Modification.


This unit is available with Silent Remote Alerting features such as vibrating pocket alert units that tell the guards which area is ‘cell phone active’ so call to discuss them first.

This unit is also available with LAN Networking to alert to your computers desktop; call to discuss this.


High Integrity vs. Low Integrity facilities: Prisons, jails, detention centers, etc. are examples of low integrity persons inside them (inmates) as opposed to business, industry boardrooms, military, government and other high-security facilities who employ high integrity pre-qualified personnel who occasionally ‘push the rules’ policy envelope. The proper ways to deploy a cell phone detection system in the high-integrity facilities are nearly identical to the scenario in place when you travel by air.


First state the goal clearly; We all know it is to PREVENT people from bringing unauthorized “things” into the facility as defined by POLICY. Every secure facility has exactly the same GOAL.



How Behavior Modification Works: Suppose you are going to the airport and you have a weapon in your car. Do you KNOW in advance that you will walk thru a metal detector? Of course you do! (silly question…but highly relevant) So what do you do? Bring it in anyway and “hope” no one will be alerted? No way.  You KNOW the consequences in ADVANCE for failure to comply and you KNOW you will be found. So the weapon stays in the car safe and sound.


What just happened? That is 100% deterrent factor; pure and simple. This scenario happens repeatedly every day.  The airport wins since they did NOT detect your weapon and they are happier for it even if the metal detectors are turned off they still modify bad behavior on-sight.


Consider that today metal detectors at airports, despite the fact we make a good living selling thousands of them at a cost of millions of dollars, almost never find a real weapon…they detect keys, watches, glasses, pens, change, belt buckles, etc., we all know the drill.  After all these years of them being omnipresent their role is simply to be the policy ENFORCERS who almost never really alert on a tangible threat.  They do that job very well too and everyone knows it.


We both know that you want to eliminate unauthorized cell phone use in your facility but you really don’t want the labor intensive problem of shakedown of every person on arrival with a metal detector so what to do?


For those of you in a “high integrity” environment employing smart folks who will push the rules policy as far as they think they can get away with it but put up a Cell Phone Detection system and the results are quite dramatic. For example I know that if I am dumb enough to walk into that facility with this thing in my pocket they are going to find out about it…so the result is I leave it in the CAR…problem solved. OK I am not stupid but I will sure bend the rules if left to my own devices. Deterrent factor detectors with in-your-face high visibility altered the behavior pattern and the goal is quickly attained.


50% detection and 50% deterrent solves both issues: We put these in all the time…for a while the detectors alert constantly…but soon word travels fast and within a short timeframe they stop alerting which is clearly telling you “the policy is being enforced quietly” and the DETERRENT factor becomes 100% of the solution just like at the airport.


Consider years ago when metal detection was first installed at airports. For a while after they first appeared people brought all manner of well-known unauthorized items there only to find them in the trash can or in the hands of TSA with the result of them missing their flight. That timeframe is now gone by but the results linger forever. Metal detectors are now at virtually every airport with almost no detection of high-threat items any longer and more detectors are sold every day expecting little or no resulting alerts.


With cell phone High Deterrent overt cell phone detection systems in place we assault your EYES and your BRAIN exactly like that annoying metal detector at the airport causing you to leave the weapon in the car. We alter BEHAVIOR patterns and we are the best in the world at it since 1996 when we invented this industry.


For low-integrity facilities: If you administer a jail or other detention facility then there are many real threats you face; one of which causes as much injury and property loss as any firearm or other weapon and that is a cell phone in the hands of a violent criminal. 


They are not affected by voice alerts or other self-policing enforcement tactics that are more than enough in high integrity facilities; the system engineered for your facility must alert you in a very few seconds and you must respond immediately; here is why.


Smuggled in phones are limited: Unless your facility gives inmates chargers and outlets then it is pretty safe to assume that their battery is finite and small. Inmates don’t walk around like teenagers with the phone on all the time hoping for a text. They leave it OFF and turn it ON only to send a quick message and then it is back OFF again as fast as possible. The goal here is to DETECT and CAPTURE that phone ASAP.


Many phones will automatically REGISTER on the network (“Ping”) when first turned on, and that is our clue to get into action. We also alert you when they send a text or dial the phone too; so now the issue is for us to tell YOU of the event and for your responders to spring into action.


Alerting methods: We need to tell your responders of the event so the solutions vary widely from facility to facility based upon floor plans, distance from the areas suspected of cell phone activity to either the responder directly (direct signal detector-to-responder) or by other means to get the event related to the response station (guard station, etc.)


We use every available method to get the signal back to the responders:



Localizing cell phone signals to any one area for rapid location and capture. These are all engineered solutions designed to fit your floor plan and facility and are typically not a cookie-cutter type of product. Please call on us for some engineering consultation to insure you get what you need, but here is a primer for you to begin thinking about before you make that all-important call:


This is a common question posed by all detention center management. The question is easy but the answer is derived from many responses from YOU and depends upon many factors:


·         Your floor plans, building design, number of floors/ tiers, number of buildings & spacing

·         Location(s) of responder posts in relation to the inmate/ cells/ work areas

·         Current infrastructure available(outlined above in Getting Signal Back to the Responders)

·         Power availability in each area to be protected


Consider the options for location-and-capture with little transmission time from inmates:


Method 1: Directional antennas and computer processed solutions



Method 2: Multiple omni-directional detectors in small zones of pickup




One example of our Hidden In Plain Sight (H.I.P.S.™) product line is this unit concealed in a common smoke detector housing that is common to see and no one suspects what is inside.



HIPS Radio Call Boxes

These common Radio Call Boxes are perfect for retrofitting older facilities with no infrastructure as the Cell Phone Detection is covertly installed inside; uses the battery power & radio signals.






Enterprise Electronics

22826 Mariposa Ave.

Torrance CA 90502


Contact Bob Burchett