Is it more dangerous to have an unsupervised mobile duress system than no system at all? This is a question any security director will have to weigh when choosing between the available mobile duress options. No matter what claims are made for a mobile duress solution, it almost goes without saying that the first requirement is that it must work. If a device has a dead battery, has been disabled, or is simply inactive, then it doesn’t matter how accurate the location capability is: No alarm will be sent at all. The only way to ensure a mobile duress system is operational is by using a supervised system on a dedicated network, designed for the purpose of reliably providing alarm notifications.

In the words of Guy Grace, chairman for the Partner Alliance for Safer Schools: “Mobile duress is a critical component of school safety that has been a priority for me for years. During my time as Security Director for Littleton Public Schools, we used mobile duress, and it was fantastic. But every wireless life-safety system must meet all the same reliability requirements as its wired counterparts, as well as all the same regulatory standards. Supervision is necessary to meet those requirements and standards.”

Supervision refers to a mobile duress system’s ability to monitor its own health. It must be able to tell you that you have complete coverage, and that everything is working properly. This requires a secure, supervised wireless network. Because reliability in a life-safety system can be a matter of life and death, there is no room for error. If any component in a mobile duress system has an issue, it must send an alert so it can be immediately resolved. This means something as simple as alerting you when a device’s battery is low, granting enough to time to replace it. It also means that the system must send alerts if one of the devices has been tampered with, ensuring that a bad actor can’t intentionally disable it. In a fully supervised system, each device will also send a constant stream of check-in messages. If the head-end does not receive a check-in message from a device in a pre-determined interval, then it will consider it to be inactive, and also send an alert.

The interval between check-in messages must be close enough to ensure that inactive devices can be replaced or repaired without compromising safety. According to Guy Grace again, “There should be no more than 200 seconds between check-in intervals, and supervision must include every device in the infrastructure.”

Complete supervision also requires a dedicated network for your mobile duress system. Because supervision alerts and check-in messages are sent over the same network as alarm messages, they must be delivered with the same life-safety level of reliability. However, a dedicated network does not mean that a mobile duress system should be incapable of integrating with the security system already in place. In fact, the opposite is true. It should be flexible enough to allow it to be used with virtually any existing security system, and integrable enough to allow for a variety of responses. For instance, when a mobile duress alarm button is pressed, it might be configured to initiate the school’s lockdown procedure. But the assurance that the system is operational, and that alarms are getting through, must be the priority.

By necessity, every mobile duress system relies on wireless protocols to transmit alarms. Mobile duress solutions that use wireless technology that has not been designed for life safety, such as WiFi and Bluetooth, can sometimes provide location, but not the reliability to ensure the alarm messages are delivered. And if those systems are unsupervised, there is no way of knowing if alarms are being missed, or if the system is even operational. Mobile duress apps on cellphones are probably the least secure option. Not only are there the challenges of coverage which we’ve all encountered using our cell phones, but there is usually a complete lack of supervision. If a phone’s battery dies, or loses its connection, or the app crashes, there is no way of knowing. These are combined with the logistical issues inherent to using a cellphone itself; because any mobile duress device must be immediately available, a password or pin-protected phone is of little use in an emergency.

A mobile duress system must be designed for the purpose of life safety and use a wireless protocol appropriate to it. We use Bluetooth for transmitting music from our phones to our earbuds; Wi-Fi for streaming media; Zigbee and Z-Wave for home automation; and we have come to assume cellular coverage no matter where we are – even though we are often disappointed – but none of these were designed for life-safety applications. They are typically unsupervised, and just don't deliver the level of reliability required.

This is not a fault in any of these other wireless protocols; life safety is just not their purpose. Wi-Fi and Bluetooth were designed to move large amounts of data over relatively short distances, but as we all know from common experience, neither handles obstructions very well, and coverage can be spotty. Each is excellent at what it was designed for, but not for life safety. A life-safety system requires a secure, supervised wireless network, removed from the common faults and down times from which other wireless connections suffer.

A life-safety system is designed to move small amounts of data – alarms and alerts – over moderate range in commercial environments, using a frequency-hopping, spread-spectrum technology that sends redundant messages across multiple channels to avoid interference and obstacles. The system network must ensure that high-priority alert and alarm messages are delivered without interference, and without interfering with other systems in place. As Guy Grace, who has installed mobile duress systems in his own schools, puts it, “A properly-installed, dedicated mobile duress system will not interfere with other wireless systems the school is using – not the school’s Wi-Fi, radio interoperability system, or even other wireless security technology.”

To ensure the delivery of both supervision and alarm messages, the wireless backbone of any mobile duress alarm system must also be designed to guarantee multiple paths from the alarm device to the receiver. Usually this is achieved by installing a network of devices, called repeaters, which listen for messages and then re-transmit them to the head-end. In the words of Guy Grace again: “Each device that doesn’t transmit directly to the head-end, needs to have at least two paths to transmit its signals. That way if one repeater goes down, the signal is sent using a second repeater.” Moreover, each of those repeaters must themselves be supervised, so alerts can also be sent if one of them is tampered with or goes inactive.

Whether it be a repeater, one of the mobile duress pendants, or even the gateway itself, every component in a mobile duress system must be supervised. Without complete supervision, there is no assurance that any message sent will be delivered, rendering the system useless in an emergency. There are a number of options for mobile duress on the market and choosing between them can be difficult. But the most important consideration must be the reliability that comes from a supervised, dedicated network.

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