Install a PBX at home

Have fun with your phone ! why a pbx ? | basic configuration

Why a pbx ?

picture from wikipedia

A pbx (private branch exchange) does the work of operators in the olds days: it connects phones together. Here are some reasons to install a pbx at home:

you have two phone lines : the one from the historical operator, one from your adsl box,

you have two phones you would like to connect,

you want to program your answering machine,

you would like to check your answering machine on the web,

from anywhere in the world you would like to ring phones in the house for free just using an internet connection.

If you are interested in one of the items above, you might consider installing a pbx at home.

Basic configuration

Hardware
First of all you need an old computer, on which you can install linux. Then I bought two Digium Wildcard X100P FXO cards on ebay from ngnsky. Current price for each card is $19.99, but it was cheaper from ebay. I bought two cards since I have two phone lines (one PSTN and one ADSL). Then I bought for 60 euros the linksys pap2 phone adapter which enables to put two standard phones I already had in the house to the computer.

Software
For the software I used a linux system with asterisk. Since I am familiar with gentoo I juste typed emerge -av asterisk zaptel. I just had to compile the alsa modules with oss support in the kernel. I guess it works fine with any linux distro. If you do not want to install a linux box it looks like there is an already installed system named "asterisk now" available from asterisk.org, but I did not tried. You can check the installation of the cards using:

>ztcfg
Zaptel Configuration
======================

Channel map:

Channel 01: FXS Kewlstart (Default) (Slaves: 01)
Channel 02: FXS Kewlstart (Default) (Slaves: 02)

2 channels configured.

Configuration

First thing I want to do is: all incoming calls will ring the main phone in the house, and outgoing phone calls will go to ADSL line. Here is my /etc/asterisk/extensions.conf file:

[globals]
ADSL_LINE=Zap/1         ; i plugged my adsl line on the first FXO card
PSTN_LINE=Zap/2         ; i plugged pstn line on second FXO card
CONSOLE=Console/dsp     ; this is the asterisk console
MAIN_PHONE=SIP/home     ; name of the linksys PAP2 phone
PHONE_AT_WORK=0169081234

;
; default context is where incoming calls go
;

[default]
; make all incoming calls ring the main phone in the house
exten=>s,1,Dial(${MAIN_PHONE})

;
; local context is used by the console only
;

[local]
; dialing 666 on the console rings my phone at work
exten=>666,1,Dial(${ADSL_LINE}/${PHONE_AT_WORK})
; dialing 200 on the console ring the main phone in the house
exten=>200,1,Dial(${MAIN_PHONE})
; directly dial number beginning with 0 to adsl line
exten=>_0XXXX.,1,Dial(${ADSL_LINE}/${EXTEN})

;
; internal context is for phones in the house
;

[internal]
; directly dial number beginning with 0 to adsl or pstn
; store the extension in variable MY_EXTEN
exten=>_0XXXX.,1,SET(MY_EXTEN=${EXTEN})
; if adsl line is available try to ring it
exten=>_0XXXX.,2,Dial(${ADSL_LINE}/${MY_EXTEN})
; in case of a time out (adsl down) try pstn
exten=>t,1,Dial(${PSTN_LINE}/${MY_EXTEN})

Here is my /etc/asterisk/sip.conf file to connect the Linksys PAP2 device to the computer:

[general]
context=sipdefault
srvlookup=yes
bindport=5060
bindaddr=192.168.0.4

[home]
type=friend                       ; this enables to send and reveive calls
username=siplogin@192.168.0.4     ; 192.168.0.4 is the ip address of asterisk server
secret=*****                      ; replace ***** with a password
qualify=yes
nat=no
host=dynamic
canreinvite=no
context=internal                  ; tells that this sip user
                                  ; goes to "internal" context

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