I’ve been continuing to fool around with internet telephony. The last few weeks I’ve been fooling around with the GPL/open-source PBX software called Asterisk. PBX stands for “private branch exchange.” When ever your inside some organization that has phone extensions then there is almost certainly a PBX someplace nearby that is routing the calls from one extension to another and when necessary routing them out to the rest of the world.

It was trivial to install asterisk on one of my basement FreeBSD machines. But it has one of those configuration languages that only a old time phone maven could love. So mostly it’s been pain and suffering to get it do what I want. But I now have voice mail, and can dial out to the real phone system thru it. I keep breaking it in subtle ways or having mysterious lossage. Fun bleeding edge stuff.

This is a facinating example of a new hub displacing an old hub. The old hub; the classic phone system has a set of regulatory organizations that solved the severe coordination problems that the industry faced in the early years; and continues to face. The cost structures of the firms and these regulatory bodies is all in doubt now that the Internet has shown up with an entirely different cost structure.

I spend about 25$ a month on phone service at my house. If I set this all up and shifted my phone service to this new model I could probably lower that to around 10$ or 15$. So may $150 bucks a year. That gives you a sense of what the potential energy is that is pushing this transition. It also make clear that what I’m doing is a hobby and not a wily cost savings.

One part of my costs would be the cost of buying a dependable real world phone number and getting it routed to basement open source PBX. That runs about 5$ or 10$ a month. There is one charitable dude who will give you a free public phone number, but it’s in a different state so it would scare off my local calling friends.

One part of my costs would be the cost getting access out to the real phone system. That runs about 2-3 cents a minute. There are plenty of vendors who sell that service so lots of commodity pricing pressure.

Sometimes you can avoid routing a call into the real phone system and send it for free just over the internet. For example I have a friend who has bought phone service from Vonage and when I call him my PBX figures that out and routes the call directly to him without recourse to the regular phone system. That’s rare right now, but as the old system is displaced by the new system this will become a more common case.

My little hobby PBX in the basement currently doesn’t have any direct connection to the real phone system. It only talks to the Internet. I use services that other people provide. They can connect to the real phone system.

I could connect to the real phone system by buying something and wiring it up to my basement machine. Then when I made calls my PBX could decide if the cheapest route was to use the household’s real phone or to go out over the Internet.

Which brings us to an oportunity for collective cooperative actions. If I had such a card I could allow other folks with basement PBXs to call out thru my household phone. Doing that would require some amount of infrastructure to coordinate the sharing. For example I’d prefer to share my phone only when I knew that there was yet another phone in my region I could share if I needed to make an outbound call. I’d prefer to share my phone with some market aspect so that freeloading is limited. But those aren’t terrible hard problems. Similar systems have existed for a long time for faxing sharing.