Push the Panic Button

A look at three wireless options for mobile duress system transmission


Workplace violence can strike anywhere, at any time. Roughly two million Americans are victims of workplace violence every year; in fact, according to a 2006 U.S. Department of Labor Statistics Survey, nearly five percent of the 7.1 million private industry business establishments in the United States had an incident of workplace violence within the previous 12 months. Worse, these represent only the reported incidents; some studies say only one in five is reported.

While it is impossible to entirely eliminate violence in the workplace, there are measures that can greatly reduce the risk of events occurring, or reduce the risk of events escalating to undesirable outcomes.

After surveying the range of security options available to the healthcare industry — one of those hardest hit by the epidemic of workplace violence — the Institute for Emergency Nursing Research, in a 2011 study, concluded that panic button/silent alarm systems lowered the odds of physical violence.

To be effective, a mobile panic button system must provide reliable operation in demanding environments, must provide alerts immediately and must provide accurate location information and coverage — not only in visible and high-traffic areas, but also in stairwells, parking garages, underground walkways and outparcels, since these are often locations where incidents occur.

The performance of a mobile panic button system, also called enterprise mobile duress, is dictated by its underlying technology. This article will compare three of the most popular mobile panic button wireless technologies: IEEE 802.11 WLAN (Wi-Fi); IEEE 802.15.4 ZigBee; and proprietary, repeater-based, 900MHz Frequency Hopping Spread Spectrum. Each has pros and cons that must be carefully weighed.

 

Wi-Fi

What it is: Wi-Fi is the term used for high-speed wireless local area networks (WLAN) based on IEEE 802.11 specifications. This well-established, file-transfer specified technology is capable of moving large amounts of voice and data over a moderate distance — usually measured in hundreds of feet — making it a fit for mobile computing applications. Airports, hotels, restaurants, and entire communities now offer public access to the Internet using Wi-Fi.

The advantages: The main attraction to using Wi-Fi for a mobile panic button is the appeal of leveraging an existing infrastructure and the apparent versatility of the generic Wi-Fi network.

One such versatility is when a Wi-Fi-based real-time location system (RTLS) for tracking assets, monitoring patient flow, and staff services is used in conjunction with panic buttons for duress.

Establishing location: In the RTLS application, location is established by measuring the signal strength of a transmitting tag as received by multiple Wi-Fi access points to estimate the distance the tag is from those access points. A simple trilateration calculation is performed to determine location. In many instances, just knowing which access point the tag is located closest to is sufficient.

The drawbacks: For RTLS systems that use Wi-Fi as a sort of “carrier signal,” the relatively short 2.4 GHz waveform is easily interrupted by moving assets — carts, beds, equipment, etc. — and especially human bodies. In a dynamic commercial environment, the result is unpredictable signal loss, making meaningful determination of location difficult. We have all felt this effect with our own laptops, and it can be resolved by simply repositioning, sometimes as little as a few feet.

When tracking assets or people for the purpose of workflow management, Wi-Fi RTLS is preferred. For the purposes of a mobile panic button application, however, where a staff member in danger cannot afford to be outside coverage,even for a brief time period, Wi-Fi or Wi-Fi-based RTLS has its challenges.

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