[Asterisk-Users] Linking asterisk to an existing small office PBX

[Andrew Kohlsmith]

On December 7, 2004 07:51 am, Nick Burch wrote:
> Currently, our office has a 24 analogue extension PBX, and 2 ISDN lines
> providing it with external connectivity. We have several analogue
> extensions spare, but no capacity to add fancier connectors to link to an
> asterisk system (as most of the PBX linking guides detail). All our phones
> are bog standard analogue ones.

Ok so you have two ISDN PRI or two ISDN BRI?  (i.e. how many simultaneous 
calls can you make or take to the phone network?)

And you're saying you have 24 regular old phones -- the kind you can plug in 
to a regular phone jack and use normally.  There are no soft buttons or fancy 
displays or anything?

> We'd like to use an asterisk system to allow some calls to be routed out
> via a VoIP gateway. We'd also like to allow some inbound SIP calls to be
> handed to the PBX.

No problem.  Although I would not use FXS cards -- with 24 phones that is ripe 
for a channel bank, and since they're FXS and not FXS pretty much any channel 
bank you can find will work just fine; I recommend the Adit600 personally but 
they are pricier than the older Access Bank I and II (I handles 1 T1, II 
handles 2) -- ABI/IIs can handle FXS lines without any issues whatsoever.  
They don't work worth a shit for FXO ports though, since they don't have 
functioning far-end disconnect supervision (i.e. they can't tell when the 
other side has hung up).

So a T100P and an ABI will handle all your existing phones without any worry 
whatsoever.  Price: US$500 for the T100P and ~US$250 or so for an ABI off of 
ebay.

Any old Asterisk box will handle SIP phones, so as long as you have an 
ethernet card it'll work.

Depending on what you have for incoming lines (see my question above) you'd 
either use a T100P (total 3, may as well get a TE405P) or a single Sangoma 
A102u (2 T1s in 1 PCI card), or some kind of ISDN BRI card -- I am *not* 
familliar with the ISDN BRI stuff, so I'll defer that to someone else.

Depending on what your existing KSU or PBX is doing you can get rid of the 
thing altogether and let Asterisk do all your phone stuff, or try and 
integrate the two.  I have successfully integrated * with Norstar MICS (PRI 
and POTS) and am currently working on an NEC system whose model name escapes 
me at the moment.  The only reason I'm integrating them instead of replacing 
them is that the people I'm doing this for are quite fond of their digital 
phones.  :-)

-A.