January 2005 Anand Kumria

wildfire@progsoc.org

AK

I've been reading about VoIP for over 2 years now and been meaning to "implement" something. But I keep getting side-tracked. What I find is that I build up my knowledge to the level I need, get distracted and have forgotton a lot of things. These are my crib notes.

An FXS (Foreign Exchange Subscriber/Station) and FXO (Foreign Exchange Office) are two different styles ports. The telephone exchange generates FXS ports that you can plug into. Only FXO devices (typically telephones) can plug into FXS ports. Annoyingly FXO devices have FXO ports as well. They can only connect with FXS ports. The connection between an FXS and FXO port is the cable the from the wall socket to the phone socket. In that case the wall socket is the FXS port and the phone socket is the FXO port. There is a good diagram at http://www.digium.com/index.php?menu=fxsvfxo

Most hardware that I can find on the Internet, and for sale in Australia, seems to offer only FXS and Ethernet ports. That is they are adaptors for existing analogue phones, that do not connect to the phone network. Whereas I am after hardware that offers at least one FXO and an FXS port.

Grandstream Handytone 486 Contains one FXO and one FXS port Not A-ticked AUD165 (ozvoip.com) Sipura 3000 Contains one FXO and one FXS port (somewhat) Usable with Asterisk (see http://www.voip-info.org/wiki-Sipura+3000) A-ticked USD99 (telephonyware.com) AUD195 (myvoipstore.com.au) (no credit card) AUD195 (atp.org.au) (nope; too much info.) AUD205 (techtopia.com.au) (nope; too much info) AUD209 (ozvoip.com) Wildcard TDM400P ( 11 B ) Contains one FXO and one FXS port Not A-ticked USD193 (telephonyware.com) USD195 (asterisk.org) AUD325 (ozvoip.com) Wildcard TDM400P ( 22 B ) Contains two FXO and two FXS ports Not A-ticked USD321 (telephonyware.com) USD321 (asterisk.org) AUD530 (ozvoip.com) Octtel SP4220SO Contains two FXO and two FXS ports Not A-ticked AUD499 (ozvoip.com) Octtel SP4220DX0 Contains single FXO and FXS port Not A-ticked AUD339 (ozvoip.com) VoiceTronix OpenLine4 Contains four FXO ports A-ticked USD595 (telephonyware.com) n

I ended up buying a Sipura3000 from ozvoip.com. Not because they are the cheapest but because they don't want useless information (martial status!) and accept orders with a credit card. Hardware delivered 3 days later — so I was pleased.

Since I'm on Debian, apt-get install asterisk got me something installed but without much useful information (also grab asterisk-docs). I ended up downloading the Asterisk handbook from asterisk.org and also looking over the one from the Asterisk Documentation Project asteriskdocs.org.

Installed the ztdummy module for timing information?

There are a large of number of VoIP websites out there. A lot of people get confused between the different types of VoIP (those that are toll-bypass; i.e. using FXO ports) and those that just use a handset over IP (i.e. hardware only provides FXS and Ethernet ports). voip-info.org A good wiki with lots of useful links testyourvoip.com A resource to test your bandwidth and give you an idea of how a call to various locations will sound voipuser.org Gives you access to a UK number (inward and outward)