[Asterisk-Users] offtopic - channel banks

[Lyle Giese]

An analog phone need an FXS channel unit to drive them.  An analog phone
line needs to connect to an FXO channel unit.

An analog phone goes off hook by putting a short across the tip & ring.  The
FXS or a pots line from the Telco puts battery on the Tip and
Ground(actually it's a signal return and not a hard ground) on the Ring.
The short is the signal that the phone wants to make a call or answer an
incoming call.  The telco or FXS channel unit puts out ringing current to
ring the bell on an analog phone to tell you that there is an incoming call.

FXO = Foreign eXchange Office (faces the dial tone portion of an analog
phone line)
FXS = Foreign eXchange Station (faces the phone or station of an analog
phone line)

E&M signalling using a different set of wires to transmitt the on & off
hooks from one end to the other and is not directly compatible with analog
phones. E&M signalling is used for trunking, which is one way phone calls
get between switches(which Asterisk really is and also the telco office).

Those centronic connectors on the channel bank are where the analog leads
from the channel units appear.

Lyle

----- Original Message ----- 
From: "Ilia Mirkin" <imirkin at MIT.EDU>
To: "Asterisk Users Mailing List - Non-Commercial Discussion"
<asterisk-users at lists.digium.com>
Sent: Monday, September 06, 2004 12:56 AM
Subject: Re: [Asterisk-Users] offtopic - channel banks


> While I understand everything that you have said, I'm still a little
> confused. Yes - I have what looks like a centronics connector on the
> back. So, I can do "t100p with e&m signalling" <-> "act-1241 e&m card"
> <-> what? Namely, if the E&M card deals with the T1 end of the channel,
> how do I get that to a real phone? Will it "just work" if I plug an
> analog phone onto the correct pair coming out of the connector in the
> back? If not, what is the output of the E&M card? (and, more
> importantly, what would I need to do to hook it up to an analog phone?)
>
> Thanks for clearing things up.
>
> ---
> Ilia Mirkin
> imirkin at mit.edu
>
> On Sun, 2004-09-05 at 04:31, Steven Critchfield wrote:
> > On Sun, 2004-09-05 at 03:10, Ilia Mirkin wrote:
> > > hi,
> > >
> > > i have some newbie questions about channel banks. i have an adtran
> > > act-1241 sitting around. it accepts D4 modules, and it contains a
number
> > > of e&m cards.
> > >
> > > first of all, how does this thing work? a t1 contains 24 channels, and
i
> > > noticed that the channel bank has space for 24 cards. what do these
> > > cards do? what are their outputs? the ones that are in there have some
> > > outputs on the front marked "test", but nothing else. there are a
number
> > > of wires coming out the back (48, if i had to guess), and it has a few
> > > ports on the front which seem to be able to take in a T1. am i correct
> > > in understanding that it is the card in the bank that determines the
> > > signalling style, and not the t1? as such, is there no way that i
could
> > > use it in its current configuration to have it talk with analog phones
> > > (i.e. something like t100p -> act-1241 with e&m cards -> phone)? i'm a
> > > bit unclear on the different signalling types, and their
> > > intercompatibilities.
> > >
> > > if anyone could shed any light into this, i would very much appreciate
> > > it.
> >
> > Think of the T1 as 24 digital digital pathways. The coding of each
> > pathway must be compatible on each end. With E&M cards, you signal with
> > E&M and the line will work. The cards plug into a backplane where the
> > controller routes the digital signal to the card and then optionally
> > hook up the output from the card to a connector that consolidates many
> > lines. Look for something that looks like an older 50 pin scsi D
> > connector.
> >
> > If there is 2 RJ45 jacks on the front, and 2 50 pin D connectors on the
> > back, then it is likely that each card controlls 2 lines each. If there
> > is only 1 50 pin connector, then there is only 24 channels.
> >
> > Hope that helps.
>
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