There are a couple of linux based telephony systems.  The most robust that 
I've seen is a project called Asterisk.

http://www.asterisk.org/

It includes a voicemail system that looks very full featured.

Note that it does require some specific hardware (trunk cards, FXO cards, 
FXS cards, etc.) depending on the configuration that you need.  They have 
a comprehensive list of supported hardware.

I haven't set one of these up myself yet, but I've been toying with it as 
a possible project.  There would likely be a fairly steep learning curve 
if you're not already familiar with how PBX and voicemail systems work and 
the common telecom terminology.

Asterisk is a complete linux+commodity hardware PBX system, and may be 
more than you're looking for.

For instance, a single port PCI FXO card is about $100.  That lets you
take an analog line from the telco and plug it into your linux server.  A
4-port PCI FXS card is about $300.  That lets you plug 4 analog phones
into your linux server.  You could then share the 1 analog line from the
telco between the 4 analog phones.  If you wanted you could have the telco
aim 4 numbers at that 1 analog line, and then have seperate extensions for
each of the 4 phones off of the FXS card.  

Note that the design I've detailed above has lots of functional
limitiations due to only having a single channel to the telco.  For
instance, you could conference an outside caller with several of the
internal extensions, but you could only have a single outgoing or incoming
call at any given time.  Also, Qwest likely won't aim multiple extensions
(a small number bank) at a single residential service analog line.

Of course, you can also buy cards that support ISDN digital phones
internally and cards that support T1 or multiple T1 links to the telco.  
ISDN phones are more expensive than analog sets, and give you a lot more 
functionality.  T1 service is overkill for a home system as I have trouble 
envisioning a home system that needs to support 23 or 24 simultaneous 
calls.  A 2-port or 4-port FXO card may be reasonable though.

With a bit of scripting, Asterisk can even provide some basic IVR
functionality.  For instance, you could play an announcement when someone
calls prompting the caller to press 1 for Bob, 2 for Judy, and 3 for
little Timmy, and then route the call to a particular phone connected to
the FXS card.  You could route calls to voicemail based on time of day.  
If your family sits down to dinner between 6:00pm and 7:30pm and you don't
want to be interrupted, you could route calls to voicemail during those
hours.

If you're receiving ANI from the telco (functionally, like caller-ID 
information but technically a bit different), you can route calls based on 
ANI.  Say you want to talk to your brother Ralph any time (even during 
dinner).  You can check ANI on the incoming calls.  If it matches Ralph's 
home phone or cell phone then allow the call.  All others get routed to 
voicemail.

Anyway, you can gain a great deal of functionality, but such a project
could get expensive.  However, if you're a telecom geek it's still a lot
cheaper than putting a small Siemens or Lucent (excuse me, Avaya) PBX with
Phonemail or an Octel VMX system in your basement.

Jeff


On Tue, 13 Apr 2004, Randy Clarksean wrote:

> 
> Anyone out there had any experience with using "voicemail" software on
> Linux?  I am considering using my server for voicemail (save a few $ on
> the monthly phone bill) ... I know I can go and Google a bit to see what
> I find ... but I am still no farther ahead because I have no "real"
> feedback on how it all works.
> 
> Suggestions or experience/stories would be greatly appreciated.  Thanks
> in advance!
> 
> Randy
> 
> 


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