[Asterisk-Users] offtopic - channel banks
Michael Welter
mike at introspect.com
Mon Sep 6 08:58:26 MST 2004
If you are in the US, go to your Graybar store and ask for a short
"Amp50" cable and a "harmonica". The harmonica has an Amp50 connector
on one side and RJ14 jacks on the other. For the cable, they'll ask you
the gender of the connectors at each end--you'll have to determine the
gender of the Amp50 connector on your channel bank.
Chris A. Icide wrote:
> Ilia,
>
> Think of a channel bank as a concentrator. In a single T1 channel bank,
> you concentrate 24 analog two wire phone connections into a single 4
> wire digital interface.
>
> So in your case, the RJ45 connector is for the T1 interface to Asterisk,
> the local CLEC, or whatever you intend to connect it to. On the T1
> side, there has to be several layers of signalling and encoding. Alot
> of this information is superfluous, but may help you when it comes to
> understanding your configs.
>
> Before we even talk about E&M signalling, you have the T1 framing and
> encoding. This is used to allow both ends of the T1 circuit to
> understand how the 24 channels are being configured on the 4 wire
> circuit. It's generally going to be either sf, d4 or esf, b8zs. This
> is known as the framing and encoding.
>
> Once those are agreed upon, then we need to set up the way the T1 is
> going to signal across the channels. Normal phone lines (analog) use
> voltages, resistances, and dtmf to signal what it is doing. Since a T1
> is a digital circuit we can't do that, so we need to set up another way
> to signal, so that the channel bank knows what to do when we send some
> kind of digital signal. In this case, this is the E&M signalling you
> asked about.
>
> Finally, you probably are looking for some way to plug your phone's RJ11
> connecter into the channel bank. Unfortunately it's not that easy.
> That big Centronics style connecter is where you actually have to plug
> up the phone. there are 24 pairs of contacts in that connecter that are
> associated with each channel on the T1 circuit. Historically, you would
> connect up a cable of 50 conductors connected to the centronics
> connector on one end, and then to one side a punch down block on the
> other (just a quick-connect style access device for copper wire). On
> the other side of the punch down block, you would connect the wires that
> would then run to the remote wall jacks, etc. where your phones plug in.
>
> The problem you have is wither by google mastery or just plain brute
> force testing, you need to figure out the pinout of that centronics port
> before you can connect up any phones successfully.
>
> -Chris
>
> On 10:56 PM 9/5/2004, Ilia Mirkin wrote:
> >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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--
Michael Welter
Introspect Telephony Corp.
Denver, Colorado
+1 303 674 2575
mike at introspect.com
www.introspect.com
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