[Asterisk-Users] offtopic - channel banks

[Ilia Mirkin]

I must not be explaining my question clearly. Is E&M a framing protocol
that the signal that travels "through" the T1's channels conforms to, or
is it a wire protocol that will drive a pair on the centronics
connector. If it is the former case, then what drives the pair on the
centronics connector, and will i be able to plug a standard analog phone
into it (and expect it to work)? If it is the latter, then I assume that
there is no easy way to connect an analog phone.

Thanks to everyone for responding to my questions.

---
Ilia Mirkin
imirkin at mit.edu

On Mon, 2004-09-06 at 11:33, 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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