VoIP / IP Telephony / Digital

[AdamR78]

Hullo,

 

got a question here, hoping someone here can give me advice.

 

Essentially, the college currently has an ISDN30 digital phone line coming into the school. We have used it up to now, but have reached maximum capacity on number of handsets available (i.e. number of extensions).

This wouldn't be so much of an issue, but we are building a new block, and will require an additional 40-50 handsets, which our current system can not handle.

We have three options, and am looking for advice on what to do.

 

1: Stay with current supplier, and have a VoIP system ONLY in the new block, therefor have a mixed system.

2: Move to a new supplier, and revamp the whole system. That is, VoIP in the new block and the new block, but a digital line to the outside world.

3: As option 2, but have IP telephony to the outside world, running on a dedicated adsl line.

 

Financially, 1) is cheapest, however, cost difference is not big enough to be a major factor in decision.

 

If anyone out there could help me with some advice, pros and cons of all three systems, or helpful words... please give All help received gratefully

 

Adam

[localzuk]

I'd go with an option based around number 2 myself, but instead of using a supplier, do it in house using Asterisk and a PRI interface for your ISDN30 line.

 

You're looking at about £150 per extension for an in house system, so long as you've got the network infrastructure to support it already.

 

I can't really say much about option 3 myself, as going direct out via VOIP hasn't been looked at for us.

 

Option 1 seems like a cludge. Creating a messy system that is likely to cause issues.

[AdamR78]

Option 1 seems like a cludge. Creating a messy system that is likely to cause issues.

 

This is my main worry as well. As far as i can tel, it's really only an option in the first place, as the supplier is already known to us, and we know we cn trust them.

[paul]

Need more info what is the current system? (e.g. make model of PBX - as many newer will support IP telephony via an add in)

[AdamR78]

Need more info what is the current system? (e.g. make model of PBX - as many newer will support IP telephony via an add in)

 

Hi,

 

current PBX is an AAstra Intelligate 2065, which we have been informed by actimax (current supplier) is capable of being upgraded to support VoIP via an add-in.

 

A.

[Ric_]

Before you can decide between your options, I think you need to decide whether the existing system has all the features you need (or will need in the next 3 years or so).

 

A true IP solution will give you features like:

• Hotdesking
  
• WiFi handsets
  
• All singing, all dancing voicemail (including virtual mailboxes and 'voiceforms')
  
• Easy expansion
  
• Much more
  

 

Unless you regularly call other VoIP users I don't think that the cost benefits are currently there for ditching your ISDN line.

[steve]

Its a while since I bought a phone system (but will be buying a new one this year) so don't jump on me if I'm wrong but ...

 

The number of phone lines in the school isn't limited by the incoming line but by the PBX. Only the number of simultaneous external / incoming calls is limited by the incoming line. An ISDN 30 line can support between 8 and 30 lines into the school.

 

The incoming line has only a small part to play in deciding whether to choose a VOIP system over a standard PBX. If using a VOIP system calls to the outside world are made via a VOIP to ISDN gateway.

 

VOIP systems can use you IP network, therefore simplifying infrastructure while making the phone system more flexible and scalable.

 

We are looking at a future partial rebuild and I see VOIP as the way forward for us.

 

By replacing our existing (at capacity) PBX with a new VOIP system, we will be able to use our existing IP network to replace all existing extensions.

 

And when we start building it will be easy to add these in as part of the IP network.

[Bruce123]

Ok so this view come about 6 months too late for this thread. But we replaced our old Mitel phone system 4 years ago, with Siemen's HiPath 3000 series system. The HiPath system was designed in the 90s, and didn't orginally support IP, but the system has been upgraded to support IP using a card.

 

We use around 80 telephones and chose digital (not VoIP) purely due to the cost of the VoIP handsets (which from memory were about £200 each), and we couldn't see much benefit anyway.

 

It was the the right decision as the digital handsets work fine and can utilise the CAT5 cabling infrastructure. We'd also have to pay an additional £55 per IP device for IP licenses. We found this out when we added 10 IP telephones to a new site which was on the other side of a WiFi bridge, so could not be pathed directly into the phone system.

 

Thanks,

 

Bruce.

[localzuk]

Why did you replace an old system with a new, old, system?

[plexer]

It would be good if the op could do an update on what they did.

[Bruce123]

Why did you replace an old system with a new, old, system?

 

That's funny (really). No, the old system (Mitel) didn't work. The newer old system does work.

 

It might be based on a 90s design, but the hardware and software updates have kept it current. The feature list is quite good.

 

Thanks,

 

Bruce.

[kylewilliamson]

My ex-employeer replaced an older LG GDK-100 rig up with an Avaya IP Office 500 this previous summer. Despite what the name implies, this system could support digital, ip or plain analogue handsets and has the added advantage that both the digital and ip handsets look the same and work in exactly the same way.

 

As far as outgoing calls on ISDN-30 goes, you'd need a huge amount of bandwidth to push 30 calls at once around. Generally, as a poster said earlier i couldn't see much benefit unless you were calling other IP users or international calls. You should be able to get a really good deal these days with regards to calls on an ISDN-30 from a multitude of providers.

 

It's worth thinking as well that you do need alternative provision if the power fails. This is one area where VoIP handsets - do fall out - you need decent UPS on the PBX itself, switchgear etc all across the site. Instead of this, we installed a couple of BT lines in key locations with phones that don't require external power.

 

Kyle

[localzuk]

My ex-employeer replaced an older LG GDK-100 rig up with an Avaya IP Office 500 this previous summer. Despite what the name implies, this system could support digital, ip or plain analogue handsets and has the added advantage that both the digital and ip handsets look the same and work in exactly the same way.

 

As far as outgoing calls on ISDN-30 goes, you'd need a huge amount of bandwidth to push 30 calls at once around. Generally, as a poster said earlier i couldn't see much benefit unless you were calling other IP users or international calls. You should be able to get a really good deal these days with regards to calls on an ISDN-30 from a multitude of providers.

 

It's worth thinking as well that you do need alternative provision if the power fails. This is one area where VoIP handsets - do fall out - you need decent UPS on the PBX itself, switchgear etc all across the site. Instead of this, we installed a couple of BT lines in key locations with phones that don't require external power.

 

Kyle

 

You wouldn't need a 'huge amount of bandwidth' for 30 calls... If you were using G.711 (PCM) as the codec (which is a worst case scenario, as it is uncompressed, and has high bandwidth demands, compared with something like G.723.1 (ACELP)) and were using a packet duration of 20ms, you would need 2500kbps bandwidth to support 31 lines. Switch to the codec I mention above, and that drops to 500kbps...

 

UPS provision isn't difficult for a VOIP solution. Simply UPS the PBX, and the PoE switches which you have handsets plugged in to.

 

One of the main issues I have with hybrid solutions is that they add complexity to a system. So when something breaks, the diagnostics can take much longer whilst the source of the issue is located.

[andyrite]

Hi,

 

current PBX is an AAstra Intelligate 2065, which we have been informed by actimax (current supplier) is capable of being upgraded to support VoIP via an add-in.

 

A.

 

WE have the same system and added in VOIP later. Works really well in mixed mode. I've been using a office 70ip for over a year now with no problems.

 

 

Andy

[Bruce123]

WE have the same system and added in VOIP later. Works really well in mixed mode. I've been using a office 70ip for over a year now with no problems.

 

 

Andy

 

I have to concur (if that's how to spell the word) re mixing TDM digital phones with VoIP phones on the same system (in our case HiPath IP 3550). We've not had any problems with it. The telephones look and work in exactly the same way (from the user point of view) and configuration/administration (e.g. forwarding, pickup groups etc.) is done in the same way as well (transparently). The only difference is how you set them up in the first place (like assigning an IP address/ext number).

 

IP phones do have one key advantage in that they will work on any physical site as long as it has IP connectivity (e.g. over Routers and WAN links) to the the Phone system, whereas digital TDM handsets need to each be patched directly into the a phone system.

 

Thanks,

 

Bruce.