Get in touch with us at or contact on 0344 412 8050

Customer Portal

Frequently Asked Questions


Why choose VoIP?

Voice over IP provides major benefits to both service providers and end users: Substantial cost reduction for service providers and enterprises, Increased revenues for service providers and Enhanced productivity for end users.

What is Skype? Is this VoIP?

No, Skype is a free software programme that utilises a pier to pier Voice over IP application, meant for home use and not stable or secure enough for business. Skype is an application driven by a windows OS. Criticisms of Skype stands due to its "closed" architecture, and if you have a more powerful machine it may take over some of the machine's resources to become a "node" and support the calls of other Skype users. Skype does not use pure SIP and so is will not allow users to choose universal providers or equipment.

What do I need for a basic VoIP deployment?

pbxnsip software, Internet connectivity and a broadband router or modem. You will also need a minimum single core PC, laptop or server and an IP phone. For multiple IP phones a power over Ethernet switch will be needed. Softphone are an option instead of an IP phone. You could also have the option of deploying a single or multiple hosted account from an ITSP for which you will be able to connect back to the ITSP server and utilise the functionality on their platform.

What type of Internet connection do I need for a SIP trunk ?

VoIP is dependent on connectivity so a broadband connection is vital. G711 codec will generally need at least 64 kbps download plus 64 kbps upload bandwidth to make a single uncompressed VoIP call.
If you use compression codec's such as G.723 or G.729 the bandwidth can be compressed to approximately 20 kbps per call. It is recommended that voice have dedicated connectivity and data be kept separate from the VoIP bandwidth in use.

Which VoIP provider should I use?

VoIP is still relatively new in the market place and a stable platform is essential for business continuity, SIP providers can often be based on free software which can be unreliable if deployed incorrectly.

How good will the sound quality be?

You need to consider bandwidth and speaker quality when looking at audio. You are better to invest in good quality IP handsets in order to take advantage of products on the market that offer HD Voice and that's use reliable components. Please see the Interop page for pbxnsip compatible handsets.

Which IP phone should I get?

Please Interop page for pbxnsip compatible handsets.

How difficult is it to get an IP phone working?

pbxnsip configuration is quite straight forward, you will need account, password, registrar and outbound proxy. Configuring a handset can be found on the wiki:

Does my computer need to be turned on to use VoIP?

Only when using a soft client. If the IP PBX is on a Server, this must be switched on.

Can I call any numbers using VoIP?

VoIP is no different than traditional telecommunications. You can call any PSTN number or mobile number using an IP PBX or Hosted account. An IP PBX has the added benefit that SIP calls offer cheaper rates than PSTN minutes and that line rentals are much cheaper.

Can anyone call in to a VoIP phone?

Yes. Given that the extension is active and registered correctly on the pbx and on the IP Handset then you will be able to accept calls from both other VoIP and PSTN users. VoIP also offer the benefit that you can purchase a traditionally geographic number such as an 0161 or 0113 and this can be registered/directed to any IP PBX, IP Address or Hosted account in any geographic location worldwide.

Are their phones available to work with my Wireless Access Point?

Wi-Fi technology is dependent on the strength of signal of the access point, however yes some mobile devices and IP Dect handsets support SIP, Symbian software on some Nokia mobile phones are SIP and GSM enabled as well as some blackberry and windows mobile devices having in built SIP client.

When I travel, can I use my VoIP phone or soft client with me and use it?

VoIP registrations whether a SIP client or IP Handset are dependent on connectivity, so providing that there are no firewall issues, you can plug and play on any internet connection with enough bandwidth.

How reliable is VoIP equipment?

There are many IP hardware manufacturers established in the market place and buying cheap equipment can often mean that budget components are used, it is advised to purchase quality kit in order to avoid disappointment and issues.

Can I use my computer when I'm using an IP phone or a softphone?

It is advisable to separate voice and data when deploying VoIP solutions however if mixed then CPU usage and bandwidth are affected by active programmes, email and internet use, data takes priority and can terminate an active call or cause one way or no audio.

Can I transfer my existing telephone number to my VoIP provider?

This varies and is decided by the provider. Most SIP numbers cannot be ported away from the ITSP one registered.

Can I dial emergency numbers with my VoIP phone?

Yes, however this depends on how you are terminating your calls.

Will my VoIP phone work when there is a power failure?

Only if you have a generator backup for your network. VoIP equipment is dependent on electricity. Some gateway manufacturers allow for PSTN resilience and will take power from the legacy network.

Can VoIP use Fax?

Yes, pbxnsip is T.38 compliant however a fax to email or an ATA (analogue terminal adapter) is preferred by most users.


Why chose SIP?

SIP or session initiation protocol is a generic standard that allows for compatibility with other SIP based products offering flexibility and options to create a solutions that caters for your own needs.

What is a SIP Service Provider?

A SIP Service Provider is a company that provides IP communication through the SIP standard, also known as an ISP or an ITSP. Internet Service Providers and IT Service Providers often offer SIP termination and origination services including IP minutes and SIP accounts.

What is a SIP account and where can I get one?

SIP protocol depends on a user name, password and a domain name, very similar to an email address. Each SIP address is generic and allows users worldwide to communicate through voice, data and video, or even instant messaging. SIP address can be purchased from a SIP Service Provider or you can set up your own SIP server.

Does SIP communication work with any Internet Service Provider (ISP)?

Yes, SIP communication is dependent on bandwidth not the provider.
Some ISP's may chose to block SIP traffic, in this instance you will need to contact the provider and ask them to unblock this restriction.

What is a SIP capable firewall?

A SIP capable firewall allows for SIP communication to pass through specific ports whilst still providing security for your network. pbxnsip communicates on SIP port 5060 and SIPS port 5061.

Why do I need a SIP capable firewall?

It is not needed in all cases, it all depends if the provider is using a Session Border Controller. Pure SIP based applications are dependent on full data packets being sent and received, interruptions such as port closures, firewall blocking and NAT can mean that the user experiences poor audio quality and packet loss that can result in call dropping.

What is a SIP server?

pbxnsip is a SIP server. It is the main component of an IP PBX. The SIP server acts as an intermediary between the network and the calls. A SIP server can also be a SIP proxy and/or a Registrar.

What is a SIP Gateway?

A SIP gateway is a term used for a Media gateway used to convert SIP protocol invites and requests to a communication language compatible with legacy phone systems or to deliver traffic to the PSTN.

What is a SIP Phone?

A SIP Phone is a term used for an IP Telephone capable of speaking SIP. Examples are Snom IP Range and Polycom IP Range of telephones.


Where do I download pbxnsip?

You can download pbxnsip IP PBX software from the Downloads section of the website.

What Operating System do I need to use with pbxnsip?

pbxnsip is compatible with Windows, Linux and Mac

What is Paging?

Paging means a one-way audio communication from one caller to a potentially large group of listeners

What is an Auto attendant?

Auto Attendant is seen as an automated receptionist.
Its purpose is to offer the caller options for call redirection to a specific user, agent group, IVR, voicemail box etc. Normally they have options like "For sales press 1, For Accounts press 2 ... etc"

What is a Hunt Group?

A hunt groups forks a call sequential and parallel in order to locate an extension that can pick up an incoming call. Operates through 3 stages with time specific ringing periods, final stage handles the movement of the call to any other account or voicemail.

What is an Agent Group?

Agent group is used as a call queuing system to dispatch inbound calls to the agents in a designated order

What is an IVR Node?

IVR Node is a function used to playback a prompt allowing the user to enter DTMF digits to navigate through the PBX functions.

What are Service Flags?

Service flags are used to indicate the state of the pbx i.e. Night Service.

What is Out Bound Proxy on a Trunk?

An outbound proxy is the setting that tells the PBX where to communicate to for this call. This can be an IP Address or a domain name. Should the Outbound Proxy be set, it will restrict inbound calls coming in from the declared destination only, this can increase security of your PBX.

What is Call Back?

Calling Card / Call Back allows the user to authenticate themselves with the pbx remotely from a mobile or external device to enable an outbound call to be made using the IP PBX.

What is a Conference or a Conference Room?

It allows several participants to call in to an extension and communicate together using voice conference mixer.

What is a Dial Plan?

A dial plan is designed to route calls if they don't exist on the PBX. The routing logic within pbxnsip is to see if the number dialled is held locally within the domain, if it is, call that number. If the number dialled is not held within the domain, the PBX will send the call to the Dial Plan associated with the account. Here the dial plan is used to match certain routing criteria configured by the administrator. A dial plan can be easy or complex, it all depends how you need to configure your call routing on the PBX.

What is an Gateway?

A media gateway is a device that sits between the PBX and the PSTN network. pbxnsip communicates with the media gateway using a Trunk.

What is a trunk?

A trunk is a method of receiving and making calls from and to the PBX from the outside. Calls TO the PBX will be received on a trunk from any type of device such as a gateway, ITSP SIP trunk or another IP PBX. Calls from the PBX leave on a Trunk and could go to any device such as a Gateway, IP PBX or an ITSP SIP trunk.

What is Voicemail?

Voicemail is included with pbxnsip on each extension. When your phone is not answered, the voicemail will start and offer the option to leave a message for you.

Can I copy or move a voicemail message from my extension to another one?

Yes, when you listen to the message, there is an option to copy or move the message. You can even copy it to multiple parties.

Can my mobile phone be called when I get a voicemail?

Yes, as long as you have a cell phone mapped to your extension.

Can I have my cell phone called at the same time as my extension?

Yes, simply map the cell phone number to the extension, set the times it can be called and the delay time (if required) the cell phone should start ringing once the desk phone is ringing and the PBX will now fork the call to your mobile.



Claritel's promise to provide us with a tailored bespoke package at a very competitive rate was delivered and I'm pleased to say that we are extrememly happy with our new service provider. we signed up for IT telecoms & broadband Service at the time of our office reloacation and they helped and supported us fully throughout the transition over and above our expectation.
The Team have provided us with fantastic customer service support right from the start of the agreement and continue to support us efficiently & promptly. we are proud to support local businesses and have no hesitation recommending their services to potential customers.

CEO, Enterprise4All (North West) Ltd

Ubuntu HR
ubuntu HR ltd recently relocated our office and engaged Claritel to takecare of our phone lines and broadband. throughout the entire process Claritel & their technical team kept me fully informed as to progress and explained in a non-Jargon, non-technical way which i could clearly understand the processes etc.
Claritel took all the pain and worry out of this process and provided reassurance and an exceptionally seamless service.
They are saving Ubuntu HR over 40% on our broadband as well as the financial savings, have been an absolute pleasure to deal with.
I will be more than happy to refer Claritel to my clients, contacts, family & friends.

Managing Director, Ubuntu HR Ltd

Blackburn Rovers Community Trust
In my role as IT manager and head of business operations at blackburn rovers community trust i have had the pleasure of working with Jay & Claritel and it has been an absolute pleasure. An individual clearly on top of his game with a sound business knowledge and understanding who always goes the extra mile.
Jay and indeed Claritel as a whole has a clear understanding of its target market, what the customer needs and the best valuefor money solutions that the customer would require.
Claritel offer a wide range of services and solutions to all sectors and have a sound understanding of the perspective customers needs and can offer sound guidance and advice and are a clear example of value added, quality professionalism you would expect from a business of such stature.
I would have no hesitation in recommending Claritel Ltd
Head of Business Operations, Blackburn Rovers Community Trust