What you are asking for is pretty much what many people looking at Migrating to Asterisk in the Business world are looking for as well.
Your setup appears to me pretty Standard for a small business (SME/SMB) and as such Migrating to Asterisk can be a viable solution, however though i must caution you on this move, if not done properly it could be disastrous to the business, and since i am not too familiar with your country’s DSL network i also have to be careful at what info you are given.
The following is a Basic Guide line of what you can do, but by no means a full measure, which in any event i am sure people on these boards can correct any statements i make, or add more to it.
First of all the Equipment you will Need;
- A System to Run Asterisk on, and my advice on this is “DO not be tight, be prepared to spend a few dollars on it, after all it is running your business Telephone services”. Here is a basic system guide;
Either a very well ventilated Tower, or a Decent Rack Mount Server which has Dual Power, 1 for redundancy.
Intel Based server side Mother Board (I am biased as i don’t often work with AMD), pick a good brand such as Intel branded, SuperMicro or Tyan unless of course they are not a brand you can obtain in your country.
2GB Minimum of memory, Preferably ECC memory but not essential if you don’t have the budget. It can either be Branded RAM or Non Banded what ever you can cater for in your Budget.
Raptor based Hard Drive (I recommend Western Digital), Raptors are more reliable then the standard SATA Drive, and have more of a commercial reliability to them, plus they are fast
Intel Core Duo CPU, this will be good for when it has to place SIP based calls that are not controlled by a TDM card.
Linux Operating System, For stability i chose Fedora Core 4 but you can work with the latest release which is Fedora Core 6 can be located here redhat.com/fedora/
If your up too it, i suggest using Asterisk 1.4 it has a Nice GUI (User Interface that is good for those who can not work on the Command Line Level), and has other great features that may or may not be useful too you. If not then use either Trixbox or Asterisk Version 1.2 ( TrixBox is good but not quite the same as the full blown version of Asterisk)
I suggest a Digium Card take a look at these ones available digium.com/en/products/hardw … gcards.php they are not cheap as some other brands, but if you ask me there is nothing better then using a card that was designed for Asterisk, this way you know what your getting.
As for Phones, well you can use your existing ones or purchase new ones, which i am sure if you look over these forums you will see a few posts where you can see what is available in the market place now, or someone might be kind and post some links for you.
You will also need a Good Broadband Service, try and get one with at least a 768K Upstream capabilities, this will allow you to run multiple calls at the same time, whilst maintaining quality and integrity of the calls.
As for connecting up your Exisiting ISDN lines, then make sure you look into the Digium cards for that.
Remember, this is designed for replacing your existing PABX system which is most likely very old, having Asterisk will introduce to you a whole new world of Telephony, and your Business if don’t right can benefit from it in a big way.
However if your not Interested in building a System yourself, then i suggest you take a look around on the internet, or maybe even Digium’s website to see what setups they have, buying a pre-built system is ideally a better choice unless you have someone who can program your system up, if you don’t, working you way around Asterisk can be cumbersome and confusing to a novice.
Have a look at this and see who their re-sellers are of this product, if you ask me, this is a damn good solution then what i have proposed above digium.com/en/products/hardware/aadk.php
I know my info is not probably going to help you too much, if anything probably confused you a little more, but keep some of the info on hand as it can useful to you somewhere along the journey.