1. To set up a mini-test system can be done very cheaply. If you can't make it work little or nothing has been lost.
2. It can be configured with either IAX2 or SIP trunks. IAX2 trunks use much less bandwidth than SIP once concurrent calls are being routed over the net. This may not be an issue if you have plenty of bandwidth.
3. Remote extensions are a definite advantage of VoIP, one can connect to the PBX to make calls from home or anywhare a decent network connection is available. This is so only if the extension is an IAX2 extension! If it is a SIP extension it will not get through the firewall which your PBX sits behind. To make it do so is quite complex and simply not worth the effort! If remote extensions increase communications efficiency for the school then asterisk is the only viable option. We can supply freshtel IAX ata's they work very well and can even be used over a dial up connection to facilitate remote extensions. You could also purchase them direct from freshtel.com.au.
4. I don't know how schools work where you are. But in Australia teachers and staff are mobile within the school and often also have students offsite (excursions and camps). We have been able to connect GSM gateways to Asterisk. These gateways can be an asterisk trunk or an extension. This makes the teachers mobile an extension of the PBX.
It works very well and solves the mobility issue without relying on flakely wireless LANS and expensive or extra WiFi phones. This means staff from the school can be contacted through the PBX to mobile and vice versa. There are many advantages to this, for example parents can contact teachers when teachers are away from the school without the teacher having to give their mobile phone number. Peace of mind, security and call tracking are enabled.
Call detail records from the PBX can be used to differentiate personal from mobile calls. Mobile phones do not need Power over Ethernet supply. The UPS would only be needed on the PBX, modems and gateways.
5. In Australia we can purchase business plans from mobile phone carriers. These plans allow calls between the phones in the business group (and the SIMS in the gateway) to be free or almost free. I don't know if this applies where you are.
6. 000 OK. I just realised you are probably in Australia because you asked about 000 and not 911, but I guess you could still be somewhere else. With asterisk 000 is as easy as putting a digium card with an FXO port in the system and a dial plan for 000. Its that simple. 000 will work as long as the PBX is running.
7. Snom phones are probably an overkill to supply throughout the school, our experience is that users only actually use a small proportion of the functions available and never use the rest. Simplicity and Voice Quality are the most relevant factors. Linksys IP phones will do the job easily and provide good call quality with a quality build and feel for
a much lower cost.
8. Support, once hardware is connected support (configurations, trouble shooting, changes adds and so on can be provided remotely). Hardware failure and how quickly it can be responded to is another matter. As the IT guy I would suspect that connecting and replacing hardware would be a simple task for yourself. Once connected and mapped it would be easy for us, or anyone else to maintain.
9. Digium cards. A total IP solution is much simpler and less buggy in our opinion. But most clients wish to retain there existing PSTN phone numbers! Poring an existing PSTN number to an adequate IP provider may or may not be possible. If not the appropriate cards need to be added to the PBX or an IAD devices placed between the PBX and the PSTN.
10. Another advantage of Asterisk is that it is open source. It may also be considered a disadvantage by some. But it does mean you are locked into a particular Vendors hardware, and it's cost. As you would be aware IT is changing more quickly than ever, who wants to be locked into a single hardware supplier.
11. The real deal with VoIP is concergence to IP. As you can see we can converged mobile and PSTN telephony, we call it CommsFusion. (By the way the killer telephony costs in Australia are calling fixed lines from mobiles nad mobiles from fixed lines. These calls are never made using CommsFusion. No matter whether the caller is using a fixed or mobile handset). Further benefits accrue when telephony is fused with business applications. The opensource environment (asterisk) we believe will provide better solutions faster than closed systems.
12. So the next question is which asterisk to use! Free PBX can be stable. One of it's draw backs is changing script within asterisk, and the using trixbox at a later time to modify the PBX often cause the customised asterisk script to be deleted. We have overcome this issue, and therfore Trixbox is a real alternative, not necessarily because it is less expensive (which it is), but more importantly, modifications are easy to make and at a glance it is easy to see the status of the hardware and PBX software. Trouble shooting can be much quicker with these simple screens available.
Other Asterisk solutions are OK to.
Feel free to contact me, good luck with your meeting.