It appears you are using an older browser that is no longer supported by our website. For a better web experience it is strongly recommended that you upgrade to a newer browser. If you are running Internet Explorer, and are unable to update, we recommend using either Chrome or Firefox.

Support and FAQs

Need to contact us directly? If your question has not been answered in the FAQs below, click here to get in touch.


How does Cel-Fi Work?

Cel-Fi consists of two units: the Window Unit (WU), and the Coverage Unit (CU). Users place the WU in an area with the strongest signal from the mobile network. The CU is then either placed in the centre of the home or office, or in the area where the best signal quality is most needed. The two units communicate wirelessly with one another enabling the CU to effectively produce a 'bubble of quality signal' throughout the home or office, resulting in significantly better voice quality and greater data throughput. The WU and the CU are placed at varying distances apart, but in general an indoor distance of up to 20-30 metres is common.

Does Cel-Fi boost mobile phone signal indoors?

Yes. Cel-Fi’s mobile signal booster is specifically designed to improve indoor signal for between 20 and 30 metre radius within the building, making it ideal for homes and SME businesses.

Is Cel-Fi Legal?

Yes Cel Fi is legal. It is regulated by Ofcom and it has also been approved by certain networks. In the UK (and several other countries) Cel-Fi devices are ultimately under the control of the mobile networks, i.e. the network has the ability to disable Cel-Fi devices in a particular area, without any user input

Mobile operators have historically adopted an extremely strict policy against the use of user-installed mobile phone signal repeaters and boosters on their networks as they caused interference and damage to the performance of the networks. It is for this reason that Ofcom consider many mobile signal repeaters as illegal. Due to its unique intelligent features, Cel-Fi is the only user-installable legal mobile phone repeater permitted in the UK.

What is a mobile signal repeater and is it legal to use one?

A mobile signal repeater is a radio device that works to boost mobile network coverage for users. They amplify frequencies from mobile network providers via reception antennas. All radio devices must meet regulations set out by Ofcom. These mobile phone signal repeaters are commonly known for interfering with mobile providers and as a result, Ofcom does not licence any signal repeater in the UK, making them an illegal technology.

Cel-Fi’s technology is more advanced, allowing mobile network providers the ability to monitor and regulate the use of Cel-Fi units themselves. For this reason, they classify as a Smart repeater and are considered a legal mobile phone repeater in the UK.

What is the difference between a mobile signal repeater and a Wi-Fi signal repeater?

Wi-Fi signal repeaters (or boosters) are used to extend the coverage of your Wi-Fi signal in buildings that have weak Wi-Fi connection. Commonly, these are used for home users and can increase the coverage of Wi-Fi within a building to areas that are not necessarily covered by original wireless router. Wi-Fi repeaters work by using built-in wireless routers to boost the current router transmission and amplify it.

Mobile signal repeaters such as Cel-Fi, work specifically to boost 3G and 4G data and voice coverage indoors for specific mobile networks. They focus specifically on improving voice clarity and reduce dropped calls for mobiles in areas with poor network coverage, as well as increasing download speeds and improving streaming and internet browsing on mobile broadband enabled devices.

Cel-Fi has the ability to turn one bar of signal into up to 5 bars and can amplify 3G and 4G from areas in a building with stronger coverage, to other areas that have little or no coverage within a 13,000 square foot radius - ideal for businesses as well as home use. Unlike Wi-Fi boosters, Cel-Fi does not require a broadband connection.

What is the difference between the RS2, the PRO and the earlier edition, the RS1?

Cel-Fi UK currently has two models available for purchase; the RS2 model and the latest PRO model that joined the portfolio in early 2015. Both models work to boost indoor mobile signal for home and office use.

The RS2 works to boost 3G voice and data and is deployed in the UK with a configuration that allows the mobile operator whose network it is configured for to turn it off by setting particular parameters in the network.

The PRO works in the same way as the RS2, however, the box itself is more compact. It has a screen that allows the user to monitor the programming more and also supports 4G data as well as 3G voice and data.

An earlier model that is no longer supplied in the UK was the RS1. The RS1 had a lower capacity than the RS2 (RS2 has 3x the radio capacity) and was deployed to a limited extent by T-Mobile UK (now known as EE) and in small amounts by O2 UK.

In all other respects, the three models are the same. They are locked to a particular network, only boost that network’s radio frequencies and implement hardware and software algorithms that completely protect the network from the harmful effects usually associated with repeater products.

How does the RS218 differ from the RS2?

The Cel-Fi RS218 unit does all that the RS2 can, however, it uses a different frequency channel with less traffic in than the RS2 and therefore can be more suitable than the RS2 for rural areas that have issues with their signal. If you live in a rural area and are interested in finding out if the RS218 could benefit you, please call 0845 618 7249 to speak to one of our advisors.

What technologies does Cel-Fi support?

The Cel-Fi RS2 supports 3G voice and data whilst the most current version, Cel-Fi Pro, also supports 4G and LTE data.

What's the radiation level of Cel-Fi units?

So is the Cel-FI RS2 Signal booster safe? We actually test the Cel-Fi units like a phone for a SAR rating. Anything with a SAR rating of less than 2.0 is defined as 'touch safe'. Both the Cel-fi window unit and coverage unit have a SAR rating below 2.0.

Technically measuring SAR is usually only done for hand-held or body worn devices so WiFi routers generally don't have SAR ratings. In any case the power we emit is no greater in general than other consumer wireless networking devices and smart phones.

What is the range/radius of the RS2?

The range of the Cel-Fi RS2 depends on building construction; we quote 20-30 metre radius as standard, but it can be smaller or wider depending on:

  • the building construction
  • strength of the signal at the Window Unit and
  • physical separation of the Window Unit and Coverage unit (more separation = more boost)
How many devices can the Pro boost?

There is no limit to the number of devices that can be attached to the network via Cel-Fi. The number of calls the unit can support depends on how far away it is from the serving base station (shown by the number of coverage bars on the display of the Cel-Fi Window Unit). Where the coverage is weak (1 or 2 bars on the Cel-Fi Window Unit) the unit may support as little as 3-6 calls. Where the coverage is good (4 or 5 bars on the Cel-Fi Window Unit) the unit can support 20 calls or more.

Do I need a Cel-Fi unit on each floor?

The amount of coverage you get with one unit differs for every building and can be influenced by a variety of different factors e.g. thickness of walls. We recommend that you start with purchasing just one Cel-Fi unit for your building and see how this works for you. If you would like to discuss your requirements in further detail, prior to purchasing, please call 0845 618 7249 to speak to one of our advisors.

Will certain materials in my building affect the unit from working correctly?

Certain building materials can affect the coverage of the unit. Older buildings tend to use more materials and have thicker walls and therefore radius coverage can be reduced. If you would like to discuss a particular material in further detail with one of our advisors, please call 0845 618 7249.

How many units work together within the same radius?

Cel-Fi has tested two units working together correctly within the same radius. Cel-Fi cannot guarantee that loss of performance or network interference will not occur if more than two units are used together within the same radius.

How long is the plug lead on the unit?

It measures approximately 2m in length.

How do I stop an order I've made?

We process orders very quickly via an automated process, so please contact us as soon as possible! We will do our best to stop the order or make the needed changes but please be aware that any orders already processed cannot be stopped. In this case, you would be required to follow the returns policy.

My order shipped and I want to cancel.

In the event we are unable to stop the order, we can of course offer you a return service. To request this, please submit a support request for a Return Merchandise Authorization number (RMA#) from and fill out a returns form to send back to with the unwanted order. Please note: Cel-Fi will not cover return postage costs for unwanted products. For further information visit our Returns section.

I ordered by mistake.

In the case of an incorrect order, we will gladly help you place the correct order and provide you with all the details you need to return the item that was ordered incorrectly. Please contact our customer service team as soon as you are aware of the mistake to avoid unnecessary shipping costs.


What networks are compatible with Cel-Fi?

We have RS2 and Pro units available for Three, EE or O2. However, within these networks there are also Mobile Virtual Network Operators. Please see the additional networks these units can support below:

EE O2 Three Vodafone
Mobile Virtual Network Operators
  • Virgin Mobile
  • BT
  • LIFE Mobile
  • Blyk
  • Vectone Mobile
  • Lyca Mobile
  • Family Mobile
  • Utility Warehouse
  • Tesco
  • Lyca Mobile
  • Giff Gaff
  • BT Mobile
  • Lebara Mobile
  • Mobile by Sainsbury's
  • Talkmobile
  • TalkTalk Mobile
  • Truphone

Please note that MVNOs may occasionally change their host network. If this happens, please contact us about reconfiguring your Cel-Fi unit. Please also note that network operators have the right to shut down your system at any time, without notice.

Does it work with other Networks that are not listed above?

Cel-Fi is authorised for use by 137 mobile operators around the world. Of the world’s top 20 mobile operators, 13 have either implemented or are testing Cel-Fi. Cel-Fi UK only sell signal boosters configured to UK based networks. Other worldwide networks are available for a range of other countries; however, if a mobile network is not offered by Cel-Fi, the network is not available for purchase.

Does a Cel-Fi system have to be activated or provisioned on in the mobile operator's network?

No, Cel-Fi products do not require network activation or provisioning.

Does Cel-Fi require maintenance or adjustments if changes occur to the serving mobile network?

No, Cel-Fi does not require maintenance, and it will automatically adjust to changing cellular network situations.

Does the RS2 unit I purchased for Orange or T mobile with the SD card work with EE?

Remove and discard the SD cards, then update the Cel-Fi device to the latest operating software and configuration for EE: go to and follow the instructions.

Is Cel-Fi operator or service provider specific?

Yes. Each Cel-Fi system is customised to work on an individual operator network.

Can you reconfigure the unit’s network if you change mobile networks?

Cel-Fi units can be reconfigured by Nextivity from the network the unit is programmed to. A fee will be charged to do so.

Does the Cel-Fi work for multiple networks?

No. Cel-Fi is configured to one network at one time. Whilst it is possible to reconfigure the network on your Cel-Fi system, you will only ever be able to boost one network at one time.

Does the Cel-Fi RS2 work with 4G?

Cel-Fi RS2 will only improve the 3G signal and it's not 4G LTE compatible. It's worth mentioning that 4G is currently a 'data only' service, i.e. for Internet, downloads, video streaming etc. - the moment you make a phone call, your phone will revert to 3G (or even 2G) to make the call.

Will Cel-Fi work with my Apple Device?

Yes! All iPad and iPhone versions are supported by Cel-Fi systems sold on this web site.

Does Cel Fi work internationally?

Cel-Fi units are not only set to particular frequencies, but they are locked to the network identity (referred to as the 'PLMN-ID'). Therefore Cel-Fi devices typically only work for the particular country and network they are sold to. Only Nextivity can create the configuration for any given network.

I am living outside the UK and want to purchase from this site. Will the Cel-Fi unit work in a different country?

Cel-Fi offer various configurations for a range of EU networks. To find out if we can support you, call one of our advisors on 0845 618 7249.

Technical Information

What is IntelliBoost?

The Cel-Fi's IntelliBoost Baseband Processor is the first core processor designed specifically to optimise the indoor transmission and reception of 3G, 4G and LTE wireless signals. With advanced filtering, equalization and echo cancellation techniques, Nextivity has developed an embedded architecture which delivers unprecedented in-building data rates and pervasive 3G, 4G and LTE connectivity. The IntelliBoost processor ensures that Cel-Fi products never negatively impact the macro network while providing maximum coverage. By continuously monitoring the gain and making real-time adjustments, the system will never overdrive the base station or raise the noise floor.

What frequency is used to communicate between the two units (the Window Unit and the Coverage Unit)?

Cel-Fi uses channels from both the U-NII-1 (either 5.15-5.25 GHz OR 5.25-5.35GHz) and the U-NII-2 block (5.47-5.725 GHz) to communicate between the Window Unit and the Coverage Unit.

Does Cel-Fi cause significant degradation to mobile network quality as traditional repeater products often do?

Cel-Fi utilises an intelligent processor to actively adjust to the network environment. It uses multiple techniques including automatic gain control, real-time path loss analysis, and uplink signal gating to ensure that it never degrades the quality of the macro network signal or artificially raises the noise floor of the node B.

Is Cel-Fi a mobile phone signal repeater?

Mobile phone signal repeaters are classified as radio devices. They work to boost mobile phone signal, however, they can interfere with mobile operator networks and therefore are considered illegal as laid out by Ofcom.

Cel-Fi is different in that it is considered a smart repeater under the criteria set by Ofcom. A Smart Repeater (or Femtocell) is a mobile phone signal booster that is connected to a particular operator network and allows the host mobile network to fully monitor and control the device. Unlike, mobile phone signal repeaters, smart repeaters do not interfere with the mobile network’s coverage and are therefore considered a legal mobile signal booster. As a result, mobile network providers are beginning to work directly with these devices to offer them to users for improved indoor signal coverage.

What makes Cel-Fi different from other smart signal boosters?

Cel-Fi relies on intelligent, self-organising algorithms to maximise the area of coverage for users while ensuring that it does not compromise or interfere with mobile operator networks or impede other subscribers' signals. Cel-Fi does not require any new equipment or changes to existing network infrastructure, or mobile devices. Recognised for its superior design and effectiveness, Cel-Fi is the only consumer mobile signal booster authorised and approved by the communications commissions in Australia and the United Kingdom, and the first consumer mobile signal booster fully compliant with the new Report and Order for signal boosters as defined by the Federal Communications Commission (FCC) in the USA, effective from March 2014.

What is the MHz of the frequency channel for the RS2?

The RS2 runs along 'Band 1' only, meaning that the frequency channel is 2100MHz and only supports 3G.

What is the MHz of the frequency channel for the RS218?

The RS210 runs along two bands; ‘Band 1’ and ‘Band 8’ meaning that the frequency channel is 2100MHz and 900 MHz and only supports 3G.

What is the MHz of the frequency channel for the PRO?

There are many different variants of the PRO depending on the network provider.

For EE and Three, the PRO runs along ‘Band 1’ and ‘Band 3’ meaning that the frequency channel is 2100MHz and 1800MHz supporting both 3G and 4G.

For Vodafone and O2, the PRO runs along ‘Band 1’, ‘Band 8’ and ‘Band 20’ meaning that the frequency channel is 2100MHz, 2600MHz, 900MHz, 800MHz supporting both 3G and 4G.


I need some technical help with an error I am getting on my Cel-Fi PRO unit.

Please download our troubleshooting support guide and follow the instructions.

Troubleshoot support for the Cel-Fi PRO Window Unit
Troubleshoot support for the Cel-Fi PRO Coverage Unit

If the issue is still not resolved after carrying out the instructions on the troubleshooting guide, please contact a member of our customer service team on +44 (0)8456 187 249 or

I need some technical help with an error I am getting on my Cel-Fi RS2 unit.

Please download our troubleshooting support guide and follow the instructions.

Troubleshoot support for the Cel-Fi RS2 Window Unit
Troubleshoot support for the Cel-Fi RS2 Coverage Unit

If the issue is still not resolved after carrying out the instructions on the troubleshooting guide, please contact a member of our customer service team on +44 (0)8456 187 249 or

I have followed the set up instructions but I am getting an error message...
Error code Meaning Resolution
Coverage Unit Shows Value of '0' The coverage unit is too close to the window unit Move the coverage unit further away from the window unit
E4 Window unit is overheating Make sure the vents on the unit are not blocked. Move the unit to a cooler area. The system will start working normally when it cools down
E3 Coverage Unit is overheating Make sure that the vents on the unit are not blocked. Move the unit to a cooler area. The system will start working normally when it cools down.
E1 No signal on the Window Unit Try moving the window unit to another room or area where you have coverage. (use your mobile phone to find the best 3G coverage)
Red Status on Coverage Unit There is a hardware error Try resetting the coverage unit by unplugging it and then plugging it back in. If problem persists return system for a service
7 segment display on the CU is cycling for more than a minute The unit is taking longer than normal to make a link Wait for the display to stop cycling, this could take several minutes. Move away from WiFi devices
No lights on Coverage Unit display There is no power Is it plugged in? Is there power at the outlet? Try exchanging the power supplies with the window unit to see if the power supply is defective.
Centre three bars on signal display of Window Unit are flashing It means network operator data is missing. Contact Cel Fi customer services
No segment lit on signal display of the Window Unit and status indicator on solid green Cel FI is not receiving any 3G signal Move the window unit to another room or area where you have more coverage. (use your mobile phone to find the best 3G coverage)
Status indicator on the Window Unit is on solid red There is a hardware error Reset the window unit by unplugging it and then plugging it back in again. If problem persists contact Cel-FI customer services.
Status indicator on Window Unit is flashing green for more than a minute The window unit is attempting to complete regulatory compliance Wait for the status indicator to stop flashing, this could take several minutes
No lights on Window Unit There is no power Is it plugged in? Is there power at the outlet? Try exchanging the power supplies with the coverage unit to see if the power supply is defective.