We  can build a telephone exchange in our office without any cost.An exchange that we can make calls internally to phone( both soft phone and IP phones) with out having any cost.All we need is a lan connection.Got shocked!!!.

Nothing to wonder it can be make possible by “open source asterisk telephony platform” .I am not going to explain all about the asterisk but a simple introduction and how to set a small PBX in our office.

Asterisk is an open source telephony platform which can able to do all the thing that traditional EPABX can do or much more than it also supports VoIP. Or in other words we can tell it a Software PBX.

For creating a simple PBX to make calls between the soft phones we needs to asterisk installed in the system.Any Linux OS can be used for the installation.You can download asterisk from the official asterisk site www.asterisk.org

commands:

tar xvfz asteris-*

cd asterisk-*

./configure

make

make install

ok now asterisk is installed in your system.

For starting asterisk issue command:

asterisk -vvvvgc

you will get a conslole like this

Our Exchange is ready now.

Install soft phones in your friends machine .

Lots of free soft phone are available to download one such you can get form here

Ok ..now your telephones are ok .Now ne need is to assign numbers to the soft phones and set the the domain as the asterisk server IP address

Soft phone will be some thing simliar to this.

Assign number say for example.200, and 100 for two soft phone in two computers connected to the LAN which includes the asterisk server.

Edit files in the asterisk servers.

First edit sip.conf

location: /etc/asterisk/sip.conf

add these configuration

[200]
port = 5060
type=friend
context=switch
username=200
secret=200
callerid=200
host=dynamic
canreinvite=yes
disallow=all
allow=all

[100]
port = 5060
type=friend
context=switch
username=100
secret=100
callerid=200
host=dynamic
canreinvite=yes
disallow=all
allow=all

edit extension.conf

location: /etc/asterisk/extension.conf

copy paste this at end of the file

[switch]
exten => 200,1,Dial(SIP/200)
exten => 100,1,Dial(SIP/100)

Restart asterisk by giving “reload” command in the console which we get when we start asterisk.
Now your phone will get registered.Start calling from your soft phone installed in your PC to your friend.

More to learn visit asterisk.org, voipinfo