The use of cell phones in prisons presents a serious security threat. Access to phones enables the coordination of illegal activities, the harassment of victims in the community, and increases risks within the prison for both staff and inmates.
While banning devices is standard practice, phones still find their way into prisons and stopping their use requires advanced methods and technology. This article explores techniques for preventing cell phone use in prisons, including:
- mobile phone signal detection,
- ferromagnetic detection, and
- signal blocking.
Combining some or all of these methods can create a multi-layered approach to enhance prison security and reduce legal activity.
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Mobile Phone Signal Detection
An effective strategy for identifying unauthorized cell phone usage is mobile phone signal detection. Signal detectors identify and locate active cellular devices by picking up on their radio frequency (RF) signals. Using direction finding antennas, signal detectors can pinpoint specific cell phone locations within the prison identifying hidden devices and enabling seizure.
RF signal detection is an essential method for identifying cellphones in prisons. Even with other security measures in place, it is almost impossible to know if illegal cell phone usage is happening if you do not have the ability to detect it.
PROS: detects use and pinpoints location; cost-effective
CONS: does not detect unused/powered off devices
Take a look at the Comms-Tek range of cell phone signal detection technologies
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Ferromagnetic Detection
Ferromagnetic detection is another method for identifying contraband cell phones. Unlike signal detection, ferromagnetic detectors sense the magnetic fields created by metallic components in devices, allowing them to detect phones even when powered off or in airplane mode. Handheld or walk-through ferromagnetic detectors can be deployed at entry points, common areas, and specific prison zones to detect unauthorized cell phones. Because ferromagnetic detectors do not rely on a power source, they are ideal for identifying phones before inmates have a chance to activate them.
Ferromagnetic detectors can also be integrated into security screenings for visitors, contractors, and staff to prevent phones from being smuggled in. Their use ensures that attempts to evade detection by powering down the phone are countered, limiting the number of devices in circulation.
PROS: detects devices at key access points
CONS: does not detect usage or location within restricted areas
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Mobile Phone Signal Blocking
Another layer of defence is signal blocking or jamming technology, which prevents mobile phones within a designated area from connecting to nearby cell towers.
Signal jammers work by emitting frequencies that disrupt cellular networks, effectively blocking phone calls, texts, and internet access. Placed strategically, these jammers can restrict connectivity within specific parts of the prison without affecting areas beyond.
However, signal jamming can interfere with emergency communications if not carefully controlled, so it’s critical to configure this technology precisely. This can become very expensive. Some newer jamming solutions are selective, targeting specific frequencies or bands to ensure staff devices and authorized systems remain operational.
NOTE: Signal jamming is not generally allowed in most countries, and where it is, special permissions from authorities are required.
PROS: prevents use
CONS: often unauthorized, requires careful configuration
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Managed Access Systems (MAS)
Managed Access Systems (MAS) are advanced solutions that monitor and control all wireless communications within a designated zone. Unlike blanket signal jamming, MAS can selectively block unauthorized devices while allowing approved ones to connect. MAS technology identifies each device attempting to connect to a network and determines whether to allow or block access based on pre-configured criteria.
In some prisons, MAS can also log connection attempts from unauthorized devices, providing law enforcement with data to track persistent offenders or patterns of activity, potentially linking inmates to organized networks outside the facility.
MAS is expensive to deploy, run and maintain, requiring a significant initial investment and ongoing operating costs, specialist operators and service providers. This means deploying a Managed Access System is often only economically viable for very large facilities.
PROS: prevents use, highly configurable
CONS: expensive investment, high operating costs
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Body Scanners and Comprehensive Search Protocols
Body scanners are useful as a first line security measure, especially when ferromagnetic detectors cannot easily detect SIM cards or phones hidden within the body. These scanners use advanced imaging to detect concealed items and are commonly used at entry points to secure facilities. Along with regular physical searches, body scanners can help locate and deter the smuggling of phones.
PROS: practical, cost-effective
CONS: does not detect or pinpoint usage
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Manual Searches
Additionally, deploying random cell searches and using trained K9 units can add another layer of detection. Dogs trained to sniff out mobile devices are becoming an effective tool in high-security facilities.
PROS: practical, cost-effective
CONS: does not detect or pinpoint usage
Conclusion: A Combined Approach for Maximum Security
Each of these methods—mobile phone signal detection, ferromagnetic detection, mobile phone signal blocking, managed access systems, body scanners, and manual searches—has unique strengths and limitations. Mobile phone signal detection is effective for locating active devices, while ferromagnetic detection can find inactive ones. Signal blocking and MAS allow control over wireless communication, and physical searches add an extra safeguard, but economic viability and effective implementation can prove to be a challenge. To ensure the most secure environment, it is recommended that prisons use a combination of these methods, layering multiple approaches to reduce the risk of contraband cell phone usage effectively.
Take a look at the Comms-Tek range of cell phone signal detection technologies: Hunter, Scout, WatchMan.