From: Dave Gingrich (Dave@xxxxxxx)
Date: Sat May 20 2000 - 10:10:03 GMT-3
At 06:50 AM 5/19/00 -0700, Kent wrote:
>Dave,
>
>Sorry for bothering you again, just want to make sure
>I really understand this. If the PBX has a CO line on
>it, the line will be connected onto its FXO port, this
>port receives ring in, so you need to configure the
>PBX to forward the ring to either your auto operator
>or one of the extensions, say the reception, right?
Yes that is correct. However if you call it an FXO port in front of the PBX
guys, you may get puzzled looks. To them it is just a C.O. trunk port.
Foriegn Exchange (FX) to them, means a trunk coming from a non-local exchange.
>Can I ask the teleco to give me a digital line and
>connect it to my PBX? I know we can do this between
>our PBXs, but can we just ask them to give us a line
>from their system to our PBX, the line both sends and
>receives digits? In this case, our PBX will both sends
>and receives digits to the CO, is this some thing
>meaningful to you?
The short answer is Yes, if the PBX supports it. But there are many
questions to be asked and answered. In a private network (between your two
PBXs) you probably just ordered a point to point T1. How it functioned was
completely dependent upon how the PBXs on the ends were programmed. Often a
T1 just provides transport for 24 E&M tie lines or FXO/FXS. In which case
it is still important to understand all of the FXO/FXS/E&M stuff because it
describes the type and direction of the signalling. If the PBXs support
some type of D channel signaling arrangement, then the link will begin to
look like an ISDN primary rate service. A Cisco router with a T1 voice
interface can do any/all of those (the D-channel signalling interface is
called Q-SIG).
A digital line connection between a PBX and the telco today is most often
an ISDN primary rate interface (PRI). PRI is C.O. service that includes
access to the public network delivered over a T1 facility. It is two-way
dial, so it begins to look like E&M functionally, but all signalling is
handled on the D-channel, rather than in-band like E&M. You can get
standard C.O. analog trunk services delivered over a T1, but because of
enhanced features and often lower cost of ISDN PRI, it is becoming rare.
=====================
Dave Gingrich, K9DC
Indianapolis, Indiana
Dave@dcg.org
=====================
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