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Register now to access our FREE Online Technical Training Courses!

Good news! ProVu resellers can now access our online training courses for free! That’s right, there’s no catch – simply register for the courses you wish to access today and start developing your Technical Support Services.

What courses are available?
Online courses currently available include:

Gigaset DECT online training

SARK PBX online training

Snom Handset online training

Yealink Handset online training

What are the benefits?
Our online courses are designed to improve your technical knowledge across a range of leading VoIP hardware manufacturers – ultimately helping you to increase your hardware sales and support your customers more effectively!

Am I eligible?
Our online courses are technical-based, however, there are no limitations – you can register as many individuals as you like.

What’s involved?
All of our courses are divided into easily manageable chunks, enabling you to complete courses at your own pace


Find out more & Register Here


Here at ProVu, we pride ourselves on our in-depth product and technical knowledge. If you have a specific training requirement, please get in touch – we’d love to hear from you!

Using secure SIP and RTP with SARK PBX and Snom or Yealink phones

This involves two levels of encryption. The first is SIPS/TLS which is encryption of SIP signalling between the SARK PBX and your IP phone. It works in much the same way as HTTPS certificates do.

You can either purchase a certificate from a trusted source or generate your own self signed certificates. I’ll use self-signed certificates here because they are free and do the job for what I wanted.

The second part of encrypting your phone calls is the actual audio stream itself, the RTP. We can use SRTP, this is simply a case of turning it on but there’s no real point to doing this without firstly configuring SIPS/TLS because the keys used in SRTP encryption are passed in the SIP messages.

For me, there’s two reasons for doing all this.

The most obvious one is security, encrypting your phone calls means that anyone who is able to sniff your network traffic cannot extract your phone calls. For most people this is pretty unlikely but could happen all the same.

Perhaps of much more use is for remote or home workers and this is what made me get this working with SARK. One of the biggest problems in the world of VoIP is SIP-ALGs on routers making incorrect alterations to SIP packets. If your SIP packets are encrypted then any router they pass through cannot possibly make any alterations to them!

The steps to getting this working are (basically the same process on a SARK PBX as on any Asterisk PBX).

1) Generate self-signed certificates (commands issued at the Linux command prompt on SARK):

  • cd /etc/asterisk
  • mkdir ssl
  • cd ssl
  • echo 00 >
  • openssl req -out ca.pem -new -x509 -days 365
  • openssl genrsa -out server.key 2048
  • openssl req -key server.key -new -out server.req -days 365
  • openssl x509 -req -in server.req -CA ca.pem -CAkey privkey.pem -CAserial -out server.pem -days 365

2) Configure Asterisk:

Edit the file ‘sark_sip_header.conf’ either from the command line or in Asterisk File Edit in the SARK web interface. Add the following:


Replacing xx.xx.xx.xx with your system’s own IP address. The last line isn’t essential for us but means if Asterisk is connecting as a client to a TLS server (so you’d need a SIP service provider who does TLS), whether to verify their certificate or not. If you do verify their certificate then they cannot be using self-signed certificates.

3) Configure extensions:

You can specify which extensions will use TLS & SRTP (and any you don’t, stay using unencrypted SIP & RTP).

In the SARK web interface, edit the extension and go to the “asterisk” tab. Add these lines:


This will turn on both TLS and SRTP for that single extension.

It’s important to note that once you’ve applied this, the phone MUST use it and trying to Register without encryption will now fail.

4) Configure the firewall:

By default SARK PBX only allow in SIP over UDP but TLS uses TCP. You need to add a rule in the ‘firewall’ section of the SARK web interface to allow TCP port 5061 (SIPS/TLS uses 5061 by default). Note, you don’t need to allow RTP over TCP, SRTP still uses UDP normally.

5) Configure the phones:

This assumes you already have a phone configured and working using normal SIP, this is how to convert them to use SIPS/TLS & SRTP.

Snom phones (note, you’ll probably need a fairly recent firmware version)

  • In identity #, add an outbound proxy such as “;transport=tls”. Where is your SARK PBX’s hostname or IP address. You could also set up the correct DNS-SRV records for this (hint, _sips._tcp) but I’ll not go in to that here.
  • In the RTP tab, turn on RTP Encryption, set SRTP Auth-tag to AES-80 and RTP/SAVP to Mandatory

Then when making or receiving a call, look out for the little “lock” symbol on the phone screen to signify SIPS/TLS & SRTP are both in use in the call in progress.

Yealink phones (I used v72 firmware, older may work too)

  • In Account #, Register tab, set Transport to TLS, set Server Host Port to 5061.
  • In the Advanced tab, set RTP Encryption(SRTP) to ‘Compulsory’

Much like Snom, the phone will also display a “lock” symbol on the screen during a call with SIPS/TLS & SRTP in use.

One last thing to note, both Snom and Yealink phones do not verify server certificates by default. This means that there is no protection against a man-in-the-middle attack (someone else pretending to be your SIP server). You can turn on certificate verification on either phone but you MUST also do one of the following in order for SIPS/TLS to continue to work:

  • Purchase a certificate from a trusted source, much like you would if setting up a HTTPS website. Please speak to us first so we can advise you on the best place to buy as the phones have a limited number of CAs built into them in comparison to a web browser.
  • Continue with your self-signed certificate but load the CA it was signed against into the phone. This is the “ca.pem” file generated earlier on. It is safe to distribute this to your phones, it cannot be used to be generate more certificates without the key (which you need to keep safe).

Any questions to

New Online Sark Training Course

ProVu are pleased to announce the launch of an online training course for Sark PBX resellers and installers.

Online training is a new endeavour for us but we believe it will soon be an important part of our customer support package for the following reasons:

  • there’s no need to resellers to take a day (or more) out of their office
  • it can be completed in your own time over as long a period as you want
  • it is always available as a reference tool, even after completing the courses
  • training materials can be skipped if some parts are too easy or re-read/re-watched if some parts are difficult
  • no need to wait for a scheduled training day – online training is available as soon as you want it
  • no travel expenses!

This training course consists of a series of videos followed by a practical exercise and finally a multiple-choice quiz. There are four sections structured like this in the whole course.

The training is intended for technical support staff, installers and systems integrators. If you are interested in sales training then please get in touch and we’ll organise this for you.

We believe the best way of learning is by doing so this is still very much a practical training course and you will need a SARK200 PBX and some phones just like the on-site training we have held in the past.

We are likely to be running some deals along the lines of free training with purchase of a not-for-resale Sark PBX.

The online training will also be available at no extra cost to anyone who has completed one of our Sark training days in the past. Please email us to gain access.

If you are interested in our online training please email Contact or phone us on 01484 840048.

We will be releasing more online training courses in the near future so please keep an eye on our Blog and website.

Changing music on hold on a sark pbx (including sark200)

If you want to change the music-on-hold that comes as standard on a SARK PBX, the main stumbling block is getting the audio file(s) in the correct format.

There are several you can use, the best is a wave file with the following format audio:

RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz

This should work on any SARK PBX, including the SARK200.

It is also possible to use MP3 but you may need to also install MP3 decoding software and it will put a small amount of extra load on to the system.

A number of free tools can be used to convert your audio files into this format such as “sox” or “audacity”.

The simplest way of replacing the existing MoH on SARK is to connect to it using ssh/scp (or WinSCP if using Windows) and go into the folder:


Then delete or move any audio files in there and copy your new file(s) in to there.

Note – if you have an older sark system then the location will be /var/lib/asterisk/moh

Then reload Asterisk by clicking on the “commit” button in the web interface or using the command “moh reload” at the Asterisk CLI.

One last thing, you cannot use copyrighted music unless you have a PRS license. So make sure you are using music with no copyright (there are a couple of online libraries for this) or music you’ve had professionally produced.

SARK 200 Mini IP PBX just got bigger!


Since its launch earlier this year the SARK 200 has proved to be the ideal solution for small businesses and start up companies. Having all the business class features of far larger traditional systems plus the flexibility of a VoIP system to connect remote offices and home workers the SARK 200 has proven to be a real success for small and young expanding companies.

But what do you do when you out grow your SARK 200?


Upgrade your SARK 200 with a expansion licence taking it to 24 extensions.

The SARK 200 expansion licence takes the SARK 200 from its standard 12 extensions up to 24 extensions, we believe this now makes the SARK 200 the most flexible and competitively priced phone system available for small business.

The SARK 200 expansion licence is available to order for both systems already deployed as well as new systems.

Here’s a reminder of the SARK 200 key selling points:


Try a SARK 200
If you have not tried SARK or seen the SARK 200 we have a small number of samples available for evaluation on a sale or return basis. Please contact us if you would like to take a sample on sale or return.

Find out more information on the SARK 200 and its many features. Get in contact if you would like pricing information. Call us on 01484 840048 or send an e-mail to

SARK SIP-to-SIP peering

You can use the built-in SailToSail or IAX2 trunks, but both of these will use the IAX protocol. If you are wanting to achieve this sibling trunking via SIP, you will need to use the “GeneralSIP” template when creating a trunk.

The steps below are the same for both systems, so follow them through once and then repeat the same process on the other system.

– Login to the SARK web interface
– End points > Trunks > Create new ([*] button on right) > GeneralSIP
– give the trunk a dummy number (I just used 0000 in my test)

– Configure the trunk to point to the URI/IP of the target system (sibling)
– Make up a username and password
– Press “Save”

– Go back to the trunks screen and now “edit” the new trunk
– Click on the “User” tab that appears on the next page
– Set the “Asterisk User” box to be the same as your chosen username above
– the asterisk config for this trunk can then be populated into the textbox below:
Where the secret is the same as the chosen password before.
Now commit your changes and do the same on the other system. With any luck, these should now be peering correctly. You may wish to check on the asterisk console `asterisk -rvvvv` and then `sip show peers`

Best of luck!

One step closer to the Plug and Play IP PBX

SARK 500 flexibilityWouldn’t it be nice if you turned up to install an IP PBX and all you had to do was connect the lines and phones and everything just worked, with inbound calls automatically routed to the connected phones. With the combination of a SARK phone system plus snom and Yealink IP phones, it can be this simple.

Until now the reality has been quite different, the constant headache for telecoms engineers in setting up an on-site IP PBX has been in the configuring of extensions when they do not have control of the network. The largest time consuming element of any installation is the provisioning of the IP phones with the correct settings. Often getting this provisioning information to the phones has relied on special settings on a DHCP server . The problem with this is, that in most cases the telecoms installer does not have access to the DHCP server and even if they do, not all routers necessarily support this capability. The only option at this point is to manually set up each phone which is extremely time consuming and more importantly adds considerable cost to an installation.

The SARK development team led by Jeff Stokoe have harnessed a technology that has been embedded into snom and Yealink phones called SIP Multicast. During boot-up, the phones send out a SIP packet to a special IP address reserved for SIP Multicast. The SARK PBX listens to this address at all times and will respond, telling the phone where to get it’s configuration from. This achieves the same job as using the DHCP server but all the functionality is contained within the phone and phone system themselves. Therefore negating the requirement for the telecoms engineer to control the network. Furthermore, SARK will automatically generate extensions on the fly when it receives the Multicast message. The phone is then passed all it’s configuration information using an intelligent provisioning engine built into SARK. At this point the engineer has only had to physically connect and power up the SARK system and phones.

Paul Hayes, Product Development Director at ProVu Communications (the sole distributor for the SARK range of phone systems and distributor for Yealink UK) said: “The SARK system is designed to be accessed remotely, yet securely. In my mind this is essential for anyone wanting to install phone systems in any significant numbers. The zero-touch configuration system and remote access mechanisms in SARK allow engineers to manage systems without on-site visits, which significantly reduces both the installation and maintenance overhead for our resellers.”

ProVu Communications are the sole distributor for the SARK range of phone systems and the premier distributor for snom and Yealink phones.

Find more information on the SARK 500


Article published by Maarten Kronenburg from Pika technologies. View the original article

“Sometimes I enter the office of a customer and just FEEL it – something’s brewing. A few weeks ago I was in the office of Provu in Northern England (, and “that atmosphere” was in the air. Laptop computers were installed when I came in, the PIKA WARP Appliance fired up – it wasn’t going to be a meeting around a table with a firm agenda.

Provu sells software called SARK. The people from Provu had a demo ready for me of their SARK software running on the PIKA WARP Appliance. The Provu people have spent a fair bit of time on the subject which explains why they were excited. Their software is available in various configurations of course and the smallest one is now almost converted to the PIKA WAR Appliance. And I was blown away; the feature set of their software is very, very broad, the software is responsive, the screens look good, wow, very, very professional.

But what I liked best is the remote management facility that the SARK PBX offers. The unit can be accessed by a control room for a sanity check, performance measurement and more. But you can also click through to every IP device connected to the PBX and do the same thing. This is what I call “Controlled Devices”!

So if ever you don’t want to spend the (wo)man-years on developing software at this level of sophistication you’re in good hands at Provu.”

Find out more about the SARK 500

Differences between SARK and SnomONE PBX

I’m being asked which is better, SARK or SnomONE a lot at the moment. Rather than a Harry Hill style fight, I’d thought up a quick comparison list. I don’t believe either system is “better” than the other, they have their own advantages which work in certain scenarios. Horses for courses…

Advantages of SnomONE over SARK:

– 10 user version free and downloadable.

– Windows, Linux & Mac versions (nice easy installers for each although I’m yet to try the Mac version as I don’t have a Mac).

– software only (some people see this as an advantage)

– PnP snom phone config (even slicker than Adopt in SARK)

Advantages of SARK over SnomONE:

– complete solution inc hardware (some people see this as an advantage)

– supports any SIP/IAX etc… end point (snomone is basically snom phones only apart from the odd one or two periphery devices)

– extensible : you can write your own Asterisk code and modify existing code.

– 100s if not 1000s of 3rd party bits of software support Asterisk to do all sorts of things. Including call centre reporting, operator panels, call billing etc…etc…

– choice of telephony interfaces for connecting to ISDN lines.

– custom code gives options for much more complicated call routing scenarios.

That’s all I can think of right now, this isn’t an exhaustive list 🙂

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