Radio transmission is an unsung hero of access control and security. Wireless technology is secure, reliable, and convenient – all without the need for lots of invasive wiring. But many security professionals remain unfamiliar with this technology, despite how useful it can be for motorised gates, automatic doors, and more.
What is radio transmission?
Radio transmission is a type of wireless communication that sends information from one place to another using radio waves. Radio waves travel through the air and are invisible. At any point, there are millions of them whizzing all around you. Television broadcasts, walkie-talkies, and of course radio services use radio technology to transmit information.
How does radio transmission work?
There are two essential components in any radio frequency solution: a transmitter and a receiver. The transmitter generates and sends the radio signal, while the receiver picks it up and decodes in the information contained within it.
There is a vast quantity of different frequencies in the spectrum of radio waves. In the early days of transmission, transmitters sent static messages which spanned the entire spectrum of frequencies. These days, due to the huge number of radio waves being transmitted all around us, the technology has changed. Now, transmitters encode the data they’re sending onto a continuous sine wave, before sending it to its destination via radio waves. When the message hits the receiver, it is decoded into a format that can be used, such as a recording of someone’s voice, or a string of text.
How can transmitters and receivers be used in access control?
In access control, radio transmission is commonly used for wireless activation of security systems. Let’s look at an example of an automated car gate at the end of a driveway. The gate is fitted with an electro-magnetic lock at its centre.
Hidden in a control panel at the side of the gate is the receiver. The resident of the house, who is driving up towards the gate, has a hand-held transmitter in their car. If they are in range of the receiver, when they press the button on the transmitter, it generates a signal and sends it to the receiver. The receiver recognises the signal and in turn, triggers the lock to release and the gate to automatically open.
Transmission solutions are also common for automatic garage door openers, wireless access control keypads, and automatic light switches.
How to choose the right components for your project
There are a number of different factors that you need to consider when setting up radio transmission solutions, in order to ensure that your components will work effectively together. The most important thing to remember is that your receivers and transmitters need to match. Both components must work on the same frequency and both must modulate/demodulate data in the same way.
What to consider when choosing transmitters and receivers
| Number of relays and channels | A relay is a switch that opens or closes a circuit. When a valid signal is picked up by the receiver, it triggers a relay to change from open to closed or from closed to open. This change in state is what controls the action – a light turning on, a door unlocking, or a gate automatically opening. If a receiver is equipped with more than one relay, it can control more than one circuit. For multiple relays, your transmitters will need multiple channels. For example, one button to trigger an automatic gate and another to open a garage door. |
| Memory capacity | This refers to the number of different transmitters that the receiver has space to accommodate. |
| Modulation type | Modulation is the process of encoding the message into the sine wave that is transmitted. Demodulation is the reverse: separating out the original message from the transmitted sine wave. Common methods are AM and ASK. As long as both the transmitter and receiver use the same type, the message will be successfully transmitted. |
| Frequency | The frequency of the transmitter must be the same as the frequency of the receiver. This ensures that the sine waves are being sent to and from the intended components. Most CDVI transmission solutions run at 433.92MHz. |
| Encoding method | Encoding is the process of converting data into a binary signal. Some methods offer additional security benefits, such as KeeLoq® hopping code, which constantly changes the valid passcode to prevent interception. |
| Power supply | Transmitters and receivers require a power supply to function. This might be a wired power supply or a battery. It is important to ensure you have the right version of the product with a power requirement that matches the rest of your system. |
| IP rating | If your components are to be installed outdoors or exposed to the elements, you should look for IP ratings. These measure the product’s resistance to the ingress of solids and liquids that might affect performance. The highest possible IP rating is IP68. |
Getting started with radio transmission
Starting out with new technology and new solutions is never easy. Luckily, we’re here to help!
