How does radio frequency work?
All radio transmission systems consist of two primary components: the transmitter and the receiver. The transmitter takes the message, encodes it onto radio waves, and sends out the signal. The receiver at the other end picks up the signal and decodesthe message into a usable form, such as a recording of sound or video images.
What does radio frequency mean?
Radio waves oscillate from top to bottom over and over again on their journey through the air. The time it takes for the wave to complete one full cycle of oscillation is called its frequency. It is measured in cycles per second, and can also be known as hertz.
When you’re listening to the radio, tuning it to different frequencies changes the station. For example, to get to BBC Radio 1, you tune your radio to anywhere between 97-99 FM. Those numbers refer to the frequency band over which the BBC transmits its Radio 1 station. Tuning your radio to 99 FM means that the radio transmitter is generating and sending out radio waves at 99,000,000 hertz (cycles per second).
Is radio transmission useful in access control?
Yes! Radio transmission is a bit of an unsung hero in access control. It’s a flexible solution that can make life easier for installers and end users alike in lots of different contexts. For example:
Automated gates are commonly found at the ends of residential driveways or at the entrances of commercial car parks. They are usually outdoors, which can make wiring for the opening system tricky. But with the addition of radio transmission technology, everything is a lot easier.
For a residential driveway, each resident keeps a hand-held transmitter in their car. When approaching the gate, they simply press the button on the transmitter to trigger the gates to open. They drive through, and after a defined delay period, the gates close and lock again.
Some commercial car parks utilise ANPR technology. On entering the car park, the numberplate must be checked against a database of users and verified before the gate will open. On exit, the plate usually doesn’t need to be verified again. Instead, it’s common for there to be a photocell emitting an infrared beam in a line. When the line is broken by a vehicle entering its path, the gate is triggered to open. In this instance, a transmitter can be set to send its signal as soon as the beam is broken. A corresponding receiver picks up the signal and automatically triggers the gate opening mechanism.
Safety light triggers
In a residential setting, or outside public buildings or office blocks, it’s common to have automatic lighting to improve night-time visibility. Better lighting makes people feel safe at night. There are many different ways to achieve an automatically triggered light. One of those ways is radio transmission.
Install an infrared photocell on the approach to the building which emits a beam. When the beam is broken by a person walking into its path, the photocell uses radio transmission to send a signal. The signal is received by a circuit which powers the light. Often, such solutions include a delay timer that keeps the light on for a defined period of time. After that, the circuit breaks and the light turns off again automatically, until the next person approaches.
Wireless exit buttons
One of the key benefits of radio transmission is that it’s wireless. Imagine you’re installing an access control system in a listed building. Or mounting a request-to-exit button on a glass wall. How would you be able to fit the devices without leaving unsightly wires trailing everywhere? Radio transmission is how!
All you need is a universal transmitter fitted into the back-box of your exit button, and a receiver linked to your electro-magnetic/electric lock or strike. When the user presses the button, the transmitter sends out its signal. The receiver picks it up, and in turn triggers the relay that unlocks the door. No wires, minimal disruption to the building, and a neat and tidy finish.
How to wire a transmitter into an exit button
Making your exit button wireless is easy! Using the TX26-MC1 universal transmitter, all you need is a 9V battery. Connect the transmitter to the battery, then wire the Common and Normally Open black wires into the usual exit button connections. The blue wire is the radio antenna.
Now you’ve prepared a wireless exit button, why not use it to trigger an automated door? DIGIWAY door operators come with a built-in receiver for this very reason. Here, our Training Manager, Aaron, shows you how it works:
There are endless applications for radio transmission in access control. It’s a simple, handy, safe solution to a multitude of traditional challenges for installers and end users.
For high security installations, it’s important to ensure that the data being transmitted is robustly protected from interception. Find out how encrypted radio transmission works, and why CDVI’s radio solutions are all equipped with KeeLoq rolling code as standard.