Why You Want Two-Way Technology in Security Sensors

Two-way communications is commonplace in custom-installed home systems, but less so in security devices. Here's why dealers should demand two-way feedback from inexpensive sensors and keyfobs.

Why You Want Two-Way Technology in Security Sensors
Every signal from each ELK two-way sensor is acknowledged by the transceiver to ensure reliability. This also stops repeat transmissions, saving battery life. Bi-color LEDs confirm signals have been received, saving installation steps and time.

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CE Pro Editors · November 22, 2016

Home-technology integrators are quite familiar with the concept of “two-way” communications, which often entails feedback for things like metadata. For example, a touch screen might be used to control a music server, and the server in turn reports data such as the current song, album and artist.

In the case of lighting, an interface might allow users to slide a bar from 0 to 100% to dim the lights to just the right level. Meanwhile, if someone changes the settings from a light switch, the change is reflected in the interface.

The feedback can occur instantaneously because the devices are always on, always listening, always reporting.

Wouldn't dealers and their customers want similar feedback for their alarm systems? When a door is opened, you want to make darn sure that the message is received by the security panel and, ultimately, the homeowner. When a panic button is pressed, the person in need would certainly like to know that the message was indeed transmitted. Otherwise, they're likely to keep on pushing the button until someone responds.

Unfortunately, when it comes to security systems, two-way communications can be a little more challenging than with traditional home control. That’s because security sensors are built with size, price and battery optimization in mind – users don’t want to be changing batteries on a house full of sensors every year, especially when those devices are placed on ceilings and high up on the walls.

To that end, sensors have been built with RF protocols and communications schemes that minimize interactions. In the process, two-way feedback has been sacrificed in these one-way sensors, leaving the control panels to do the heavy lifting. 

For example, to determine if a sensor is still online, the panel listens for a ping from the sensors at select intervals. If those pings don’t arrive, then the alarm system knows something is amiss.

Ideally you would want the panel to be able to query the sensors to see if they’re online and doing OK, but that means the sensors would have to always be listening, which wastes batteries.

Encrypted transmissions, frequency hopping and jamming detection, enabled by ELK's two-way sensors, make it virtually impossible to lock on to the signal, providing increased immunity to hacking.

Benefits of Two-Way

Thanks to new RF technologies and communications schemes, however, new two-way sensors for the home market have been available for the past few years from vendors like ELK Products, makers of the M1 family of security and home automation panels and peripherals.

ELK’s two-way capabilities are available on a diverse range of products including motion sensors (PIRs), smoke detectors and keyfobs. The company says the two-way nature of these products can actually save battery life because feedback can be obtained instantly, letting the sensors know the message has been received and that there's no reason to keep pinging the panel.

“Conventional wireless transmitters ‘shout’ eight times, hoping to reach the receiver,” says ELK director of sales and marketing Trudy Phillips. “However, ELK transmitters stop transmitting once transmission receipt is confirmed with an acknowledgement to the transmitter. This saves the battery power required for up to seven more transmissions traditionally sent by conventional wireless transmitters.”

Also, there is visual verification on the devices themselves in the form of an LED, which indicates a message was received from a tripped sensor. With this feedback, dealers can test each sensor at the device location, rather than having to return to a keypad or app to confirm a successful transmission. 

Beyond these "convenience" factors, however, ELK's two-way sensors play an even more important role: enhanced system-wide security.

In addition to encrypting the signal transmissions, ELK utilizes frequency-hopping across a broad spectrum in the 900 MHz band. The system automatically scans and hops across 25 frequency channels, making it "virtually impossible" for intruders to lock onto the signal and thereby hack the system. The sensors comply with the UL listing requiring the detection and reporting of outside jamming attempts.

The demand for such security features has become more urgent since recent cyber attacks on smart homes.

Building Better Keyfobs & Smoke Detectors

Let’s look at a couple of important implementations of ELK's two-way sensor technology, starting with keyfobs, one of the great conveniences offered with most security systems.

Typically, users arm or disarm a system by pressing a button on the fob, but they have no idea if the message was actually received from the security system.

With two-way communications, products like keyfobs can receive a virtual thumbs up that a command was received. When a user presses the “arm” button, did the security system go into “arm” mode? If the red LED illuminates, the house is indeed secured.

ELK adds another interesting feature that can only be implemented in two-way devices: an indication of alarm status. As the user approaches the home, a steady red light on the keyfob indicates the system is armed; a steady green indicates the system is disarmed; and a red flashing LED indicates the system has been compromised and it may not be safe to enter.

We can also see the benefit of two-way communications in ELK's Sound All smoke detector (ELK-6050). When one smoke detector goes off, it signals all other smoke detectors in the home to sound, ensuring everyone on the premises can hear the alarm.

"It can also save installers a lot of hassle when it comes to meeting new fire code requirements for synchronized sounders," Phillips says.

Check out more two-way sensors from ELK in the slideshow.


Protect Your Customers and Install Wireless Security with Confidence

As homes and businesses become smarter, so should the intelligence of their security. Recent news reports have raised concerns about conventional wireless products being susceptible to hacking. Avoid these vulnerabilities by offering a wireless solution that defends against interference, hacking and jamming attacks. ELK’s Two-Way Wireless products incorporate advanced features to ensure secure transmissions, increase reliability, extend battery life, simplify installation, and provide innovative security enhancements.



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Control & Automation · Security · Keypads & Control Devices · News · ELK Products · All Topics
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