If you have an existing PABX solution and would like to just bridge between that PABX system and VoIP then this is for you. We use various gateways that can connect to various types of ports on traditional PABX systems in order to bridge between those systems and VoIP.
Irrespecitive of the gateway in use we charge a monthly fee of R 79.80, which is a type of "line rental", and then call costs on top.
Analog ports are very common. These are the normal telephone lines we find in most houses, and they are also often used by premi-cell units. From this perspective the gateways we use pretend to be a Telkom line (similar to what a premi-cell does) and can thus both send calls out to our VoIP platform, or receive calls from VoIP and pass it to your PABX.
The exact gateway in use depends on the number of ports used, with the smallest unit being a 2-port Linksys PAP2T, and the largest being an 8-port device.
These gateways are also the cheapest by far.
ISDN - BRI
This is similar to the Telkom ISDN2(a) options, each port provides two call channels, with the smallest device here having two ports. A single gateway can thus handle up to four concurrent calls.
ISDN - PRI
With this option we connect to your PABX using a ISDN PRI E1 interface which can carry up to 30 concurrent calls. Unfortunately all the gateways here use SIP which is not particularly bandwidth efficient and can most likely only carry around 10 concurrent calls on a single ADSL line, with no way of getting around that.
For higher call concurrencies we will need to make use of an asterisk server to trunk those calls using IAX/2 over one (up to approximately 44 concurrent calls) or more ADSL lines
Again the smallest device carries two ports, but as per above you will only be able to use some of the available channels.