SIP Trunks and iPBXes are more complicated than a traditional POTS* solution, in much that same way that email is more complicated than sending a letter...

It is more complicated, but like email, once it's all set up and working it is easy.

As easy as writing an email!

*POTS = Plain Old Telephone System

PBX = Private Branch Exchange
iPBX = Internet Protocol Branch Exchange

ISDN = Integrated Services Digital Network
SIP = Session Initiation Protocol


..\ VoIP / SIP Trunks

Understanding VoIP / Internet Telephony

In a traditional environment we would expect to find an Analogue PBX with an analogue (or ISDN) trunk(s) to Telkom.  The PBX could be owned or (more likely) leased.  The traditional revenue model is that the hardware is under a lease agreement providing the supplier with a revenue stream.  Telkom chagres you for calls.

Due to the nature of telephone systems changing PBXs is non-trivial, once you are in a lease you're likely to continue it.  The equipment will age.

The setup would look something like this:

Analogue PBX with SIP trunk

You're getting a Telkom bill for line rental and calls and bill from the PBX provider who you likely seldom or never see.

Adding a new Trunk

The simplest first move is to either replace the Analogue or ISDN trunk (red section) with a SIP trunk from CIS.  See Testimonial from Dave Larkan at Freshmark Systems (Pty) Ltd

At this point your per call billing will switch from Telkom to CIS.  CIS has good relationships with IS and Telkom, we buy their services in bulk, add some value and mark up and we bill out clients. 

We can do an analysis based on an itemised call bill to show what our cost for those calls would have been - once calls are routed through us we can provide real time cost information for calls dialled and we can integrate with billing systems if you charge clients for time spent on calls.

Replacing the PBX and Telephones

iPBX with SIP Trunk


Inter office - communication Higher quality calls on offices trunked together

International breakout

Better disaster recovery options

See a full list of features at /IP-PBX-SIP-Asterisk/