7 Steps to Effectively Deploying Panic Alarms: Part 1

Mobile duress systems provide an additional layer of safety to staff as well as valuable information to first responders.

<p>Employees rarely stay in one location in a campus setting. This diagram of a typical 900MHz enterprise mobile duress <br />system shows how it can protect staff anywhere on a campus, from in-building rooms to common areas to parking lots.</p>WiFi
WiFi EMD systems can be an attractive option as they are based on one of the most well-known wireless technologies and use existing infrastructure as a way to reduce initial implem
entation cost. While it is true that WiFi systems can use the existing voice and data WiFi infrastructure, that infrastructure usually requires additional build out in order to ensure reasonable and accurate coverage of a facility. WiFi systems rely on access points to footprint a facility for a mobile duress application. As a general rule, these access points should be placed about every 40 feet, which is a much denser configuration than is required for just voice and data usage. So, while some of the infrastructure may be used, there are usually additional costs associated with building out the system for total coverage.

Not only do WiFi systems share the airspace with the ongoing voice and data activity, frequently WiFi duress systems also serve as the wireless backbone for RTLS, making the traffic on the WiFi network even more substantial. This is a major issue to consider as it could mean network system performance could denigrate and the location capabilities could be diminished during an emergency. Another thing to consider with WiFi systems is that while they offer coverage within a building, they are often incapable of providing coverage to parking lots and common areas.

Infrared (IR)  
Infrared systems can offer very precise location within a building, but they are not always well suited to duress applications. IR technology depends on line-of-sight between the alarm device and a location beacon or receiver. The need for line-of-sight is a major limiting factor with IR systems because it is something that simply can’t be guaranteed during an emergency.

IR-based systems typically do not have the ability to cover parking lots or other outdoor environments as the devices are highly sensitive to ambient light and atmospheric conditions, making them more suitable for indoor use. Therefore, IR technology is best suited to provide supplemental alarm location granularity when used in conjunction with another technology.

900MHz Radio Frequency (RF)
900MHz frequency hopping spread spectrum systems (FHSS) have been used for decades for burglary and intrusion detection applications due to their reputation for offering highly reliable performance. 900MHz systems are typically based on proprietary wireless protocols that allow for secure communications on the wireless network, decreasing the likelihood of interference from, or interference with, other wireless systems. This means the critical duress system does not operate on the same wireless network as the voice and data communications, or even the asset tracking system within a facility. 900MHz systems offer a dedicated network for EMD.

The infrastructure of a 900MHz duress system is also slightly different than a WiFi or IR installation. In a 900MHz deployment, in addition to the duress transmitters, a network of high-powered repeaters is installed to provide complete wireless coverage of a campus. Repeaters can cover thousands of square feet and are unique to RF systems. The remaining components are a receiver to hear the messages from the transmitters, and a head-end solution that turns the messages into actionable notifications to a response team.

900MHz systems also depend on the signal strength of transmitted messages throughout the repeater network to define location points. This eliminates the need to install a location device at every defined location on the campus, as in the case of IR. This allows 900MHz systems to easily cover common areas, tunnels and even parking structures. The best 900MHz systems offer full supervision, which means the radio link between the transmitters and receivers are constantly monitored for low batteries, tampering, RF jamming, or if a device goes missing from the network.

Mark Jarman is president of Inovonics (www.inovonics.com) and can be reached at mjarman@inovonics.com

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