Path: utzoo!attcan!uunet!cos!howard
From: howard@cos.com (Howard C. Berkowitz)
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet bridges above 56Kb
Summary: Thin cables; ISDN
Message-ID: <4535@cos.com>
Date: 1 Aug 88 13:01:04 GMT
References: <9392@dartvax.Dartmouth.EDU> <116@ernie.NECAM.COM> <475@vector.UUCP>
Organization: Corporation for Open Systems, McLean, VA
Lines: 53

In article <475@vector.UUCP>, chip@vector.UUCP (Chip Rosenthal) writes:
> In article <4399@cos.com> howard@cos.com (Howard C. Berkowitz) writes:
> >The original T1 system used repeaters every 6000 wire feet on
> >24 AWG or larger cables;
> 
> They still are. 

    While most T1 systems do run over 24 AWG or larger, this is
 not true of new construction in many metropolitan areas such
 as Washington, DC.  C&P Telephone installs many of their new
 T1 lines on 26 AWG twisted pair with repeaters every 4000 wire
 feet; this saves copper and space in crowded metropolitan ducts.
 Note that there are products for sending DS1 signals on media
 other than twisted pair:  fiber, free-space infrared, etc.  

>That's why the suggestions of running something other
> than 1.544MHz seem a little silly to me.  There are two types of T1 lines:
> private and public.  You can use any kind of framing format you want on
> private lines, but in either case you must meet the signal requirements
> of the FCC and your carrier. 

     I hope I did not interpret anyone's suggestion as running a raw
signaling rate other than 1.544 MBPS; not doing so would make it 
extremely difficult to use commercial test equipment, etc.
 
> Unfortunately...I don't think this helps the original poster who wanted
> to connect to networks together.  I don't know offhand if any muxes allow
> you to allocate several channnels for a data channel.  If you are interested
> in making some phone calls, I could probably pull together a list of mux
> vendors from my files.

     While it's been several years since I built DS1 mux systems,
   vendors which allowed you to split a DS1 into several arbitrary
   streams above 56 KBPS included
    
     [NOTE THE DISCLAIMER!  THIS DOES _NOT_ IMPLY _ANY_ CORPORATION
      FOR OPEN SYSTEM EVALUATION!]

   General Datacomm and Timeplex.

  As a side issue, this is one of the Great Promises
> of ISDN.  Under 23B+D primary rate, you are supposed to be able to allocate
> as many 64Kbps B channels as required for your data stream.

   Since the D channel is 16 KBPS and the B is 64, the D channel does
make 48 KBPS available for monitoring and bit stuffing for pulse density.


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