Affordable Technical Help In The Home & Small Business 7 Days A Week 8am - 8pm
mini ippbx telephone system part 4

In order to start receiving calls from the outside world we need to set up some form of connectivity with a commercial provider, there are  generally three options to archive this.

Option 1 making a direct physical connection from your telephone system to a Public Switched Telephone Network provider or landline. In our case because the Raspberry Pi 3 Incredible PBX telephone system does not have a build in interface for this feature, we would need to add additional hardware. This would come in the form of an FXO (foreign eXchange Office) interface, typically FXO's would come as an expansion card specific to particular hardware. However they can be purchased in self contained units, but the costs and additional complexity may be considered disproportionately expensive in our low cost high feature Incredible PBX telephone system solution. In the event that you choose to connect a physical landline you should consider looking at the FXO hardware available from OBIHAI as they have low cost feature rich solutions that may suit your needs.

Option 2 connecting to a Internet Telephony Service Provider, with this solution we quite simply create an account with our preferred provider who will then provide us with some credentials to enter into our Incredible PBX telephone system. Once the network connection has been established and correctly configured, we will be able to receive calls from the outside world. In fact with this solution there are a number of significant advantages such as:-
∘ Reduced line / trunk rental costs, typical line cost £7 per month
∘ Reduced call tariffs (local, national & international)
∘ Easy activation & relocation
∘ Reduced cost & ease of additional channels / lines for a single telephone number
∘ The ability to have local numbers from remote locations, both national & international
∘ Increased flexibility & mobility
∘ The ability to transfer a standard PSTN number onto the an ITSP network (Porting)
∘ Easy usage monitoring methods
∘ Prepayment billing options

Option 3 connecting to a mobile network, but like option 1 this will require additional external hardware. Further more this solution may incur additional costs to ensure network reliability  

Whilst option 2 clearly has a number of advantages, it is important that we consider its weakness. This solution is reliant on having a good network connection i.e. when the network is down or bad, communications will be effected. However based on the major advantages, the ease of implementation and the realistic possibilities of building resilience into a network option 2 is by far the best choice for our basic needs.

To get started with option 2 we need to log into our Incredible PBX telephone system GUI Administration as admin. Click on Connectivity > Trunks > Add SIP (chan_sip) Trunk

mini telephone system add sip trunk


The details required to enter in the add new trunk screen will be dependent on your selected provider. You should be able to contact your provider to ask for the correct entries for this screen, for now we will go through the basic settings required for a SIP trunk supplied from Draytel.

Enter the following details

Trunk Name
(meaningful name)

PEER Details
username=8390437
type=peer
sendrpid=yes
secret=58xGA7Gcz
registerattempts=0
qualify=yes
nat=yes
insecure=port,invite
host=draytel.org
fromuser=8390437
fromdomain=draytel.org
dtmfmode=auto
disallow=all
context=from-trunk
canreinvite=no
allow=ulaw&alaw

User Context
01204123456 (incoming number)

User Details
secret=58xGA7Gcz (sip password)
type=user
context=from-trunk

Register String
8390437:58xGA7Gcz@draytel.org/01204123456 (sipidnumber:sippassword@serviceproviderdomain/incomingnumber)

To check that your SIP trunk is registered with your provider, click Reports > Chan_Sip Info for a status report.

Now that your VOIP trunk is registered you just need to tell your Incredible PB telephone system what to do when a call comes in on the number of your VOIP trunk.

Click Submit

Click Apply Config at the top of the page

Click Connectivity >Inbound Routes

Enter the basic details shown below.

Description - meaningful name
DID Number - the telephone number associated with your VoIP trunk from your provider
Set Destination - one of your extensions

Click Submit

Click Apply Config at the top of the page

You should now be able to receive calls from the outside world (for now just set the destination to be one of your extensions, but as I am sure you have guessed there are many other options such as an IVR or Ring Group)

In part 5 we will look at what we need in order to make calls from our Incredible PBX telephone system.

If you are in the Greater Manchester area and need some help setting up your Pi telephone system then contact Peter at Burytec Telephone Engineer Manchester service.

Add new comment

Plain text

  • No HTML tags allowed.
  • Lines and paragraphs break automatically.
  • Web page addresses and email addresses turn into links automatically.