VOIP Phones

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Use a standard POTS pay-phone and plug it into an ATA (which is locked in a case).

I have a BT Converse 2025 as one of my phones. One line plugs into the BT line directly, the other into an ATA.

You need to be sure that you have adequate bandwidth on your connection for VOIP.

Harry.

 

Did you think about just using one of the Skype hardware phones that are available? You don't need a computer with some of the newer hardware devices, and you can put it behind a cheap router so it's on it's own little lan with no access to the rest of the site.

 

AJ

Have you looked at implementing one of the free PBX solutions out there? When I say 'one of', I basically mean Asterisk because, although there are others, Asterisk is widely acknowledged to be the best and probably has about 90% of the 'market share' (don't know what terminology to use for open source that fits!)

I've tinkered with the idea of doing it at home, but, tbh, I just can't be arsed at the minute, and don't make enough calls to justify the time and effort. I'm sure it would be an interesting project though and, being an educational establishment, your budget is probably at or close to zero, so it might be a cool thing to try out. I've installed a distro that is specifically designed for asterisk on a VM and it was a pretty painless experience. Of course, setting up SIP, a gateway, the PBX and making sure you have the networking in place to support it probably wouldn't be as easy - but you'd score serious geek points!

 

Hi,
You can stop skype becoming a supernode with a registry entry. GRC has the info at the bottom of the page

Ozzy

 

Other points when converting to VoIP that you need to bear in mind:

If this is for 'public' use (and I'm aware a school isn't public, but it isn't close family either) then you need to make it plain that the phone will not work when the power is out.

Most VoIP providers do not provide a '999' service.

The usual calculations for bandwidth requirements won't work well on such small numbers of lines, based, as it is, on statistics. So you will need to allow for a higher requirement than normal. This will be made worse at a school, which is timetable-based, so the windows of time when the phone could be used will cause the normal statistical calculations to be even further out!

EDIT: You may want to read this article from Ofcom on VoIP.

Harry.

 

There's some good tutorials about Asterisk and an easy all-in-one solution called Trixbox here.

How many users would you envisage making calls at the same time? I believe 35kbps per call bandwidth is a reasonable guideline in judging your capacity. I'd have thought you'd have no problem from a reasonable dsl connection. But how you will manage the gateway for calls to non-VOIP phones? You have many alternatives to Skype: there are providers who will take a direct dsl link (not over the internet) to their gateway, for example, giving higher quality than internet-based calls at much-less-than BT prices.

 

aah, boarding school.

So many memories...

All those reverse charge phone calls from the payphone in the hallway...

Of course, if your parents wanted to speak to you on a regular basis, they wouldn't send you to boarding school, would they?

Spend the budget on something else, like strippers and booze!

 

35K is not unreasonable for G.729. However - there might be situations where G.711 needs to be used. That rolls in at about 82K.

Harry.

 

I can't comment on Asterisk as I've not tryed that yet, But i find 3CX to be a great small scale IP PBX solution It's very simple to setup(could be live in minitues and runs on windows) with the free edition you get 8 External lines (PSTN/ISDN/VoIP) and Unlimited extensions or for $350 you could get the SBE that comes with 16 External lines (PSTN/ISDN/VoIP) and 25 Extensions and it comes with a whole host of tricks up its sleeve AM, call queue, digital receptionist, ddi/did etc etc

 

I know at work we use G.729a as the codec, and it's fine for our needs - when would G.711 be better?

 

When you need to use a modem over VoIP. This might sound a strange thing to do, but, for exampe, fax machines are still used a lot. Modems have a big struggle with G.729, so G.711 is used for those.

Harry.