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The Telecom Digest for January 14, 2012
Volume 31 : Issue 14 : "text" Format
Messages in this Issue:
Re: Fwd: Telephone Exchange Names (HAncock4)
Re: Digital bonanza for telecoms historians (Joseph Singer)
Re: Different clock sources for STM-1 and E1 ?? (Stephen)
LightSquared in 11th-hour effort to woo Washington (Moderator)
Setback for LightSquared (Bill Horne)
former Deutsche Telecom Execs charged with bribery by SEC (Moderator)
Re: Different clock sources for STM-1 and E1 ?? (Bill Matern of NComm, Inc.)

====== 30 years of TELECOM Digest -- Founded August 21, 1981 ======

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Date: Fri, 13 Jan 2012 07:40:50 -0800 (PST)
From: HAncock4 <withheld@invalid.telecom-digest.org>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Fwd: Telephone Exchange Names 
Message-ID: <67c176ca-23bc-4163-ba94-4d915140b8e9@24g2000yqi.googlegroups.com>

On Jan 6, 10:37 pm, Bill Horne <b...@horneQRM.net> wrote:

> When dial service was introduced (typically during the period of 1910 to
> 1970), in such multiple exchange communities, customers would normally
> dial the first two or three letters of the exchange name, followed by
> the numeric digits.

The Bell System Technical Journal has an excellent 1923 article
explaining machine switching (the "panel" system) for larger cities.
The article includes the requirements of the switch and large city
switching issues.  One of the factors (among many) was to provide a
transparent interface between dial and manual subscribers; that is, a
dial subscriber would dial numbers to a manual exchange just as they
would an automatic exchange.  The desired line would be indicated by a
lighted display panel on the destination manual switchboard.  In this
way dialing procedures would not change as manual offices were
converted to dial.

In New York City, some manual exchanges had 10,500 lines; these
required eight digit dialing and the panel senders were equipped to
handle eight digits.  Also, the party-line suffix was dialed, making
for eight digits.  The manual operator's display had provision for
both.  (See pp 80-82 in the reference below); the operator's display
is in fig. 23 on pg 82.)

http://www.alcatel-lucent.com/bstj/vol02-1923/articles/bstj2-2-53.pdf




Date: Fri, 13 Jan 2012 10:03:27 -0800 (PST)
From: Joseph Singer <joeofseattle@yahoo.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Digital bonanza for telecoms historians 
Message-ID: <1326477807.86217.YahooMailClassic@web161502.mail.bf1.yahoo.com>

Fri, 13 Jan 2012 08:44:43 +1100 David Clayton wrote:

> The UK's National Archive is to digitise 165 years worth of British
> Telecom's and its predecessors' historical documents.

If only US telecoms were interested in preserving their past.  I don't
know how Verizon or AT&T is, but CenturyLink (successor to Qwest,
USWest, Pacific NW Bell, Pacific Telephone etc.) doesn't seem to be
very interested in where they came from.  Even their attitude towards
the Museum of Communications (fka the Vintage Telephone Museum) is
that it's really not important and if they decide that building is
more important for their own needs rather than preserving the telecom
past well, too bad for telecom past.




Date: Fri, 13 Jan 2012 21:23:56 +0000
From: Stephen <stephen_hope@xyzworld.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Different clock sources for STM-1 and E1 ?? 
Message-ID: <tk71h7lojg00q1stt7nklggt364ncrcgfd@4ax.com>

On Tue, 10 Jan 2012 10:01:02 +0100, René Hüftlein
<017renegade@googlemail.com> wrote:

>Hi!
>
>Maybe someone here can help me with a problem we have with our PSTN
>gateway.
>
>We receive 63 E1's channelized into a STM-1. The E1's are provided by
>DTAG (German PSTN) and are multiplexed into the STM-1 provided by
>Verizon. STM-1 directly terminates in a Audiocodes Mediant 3000 which
>demultiplexes STM-1 and routes E1's respectively.
>
>We see a huge number of Controlled Slips (one in 20 seconds) and it
>seems this condition causes fax calls to crash.
>
>We got in contact with Verizon and they told us, that they are
>receiving DTAG's E1's in sync with a PDH clock and transparently
>multiplex that into the STM-1 which is clocked by a different master
>clock. (As it is not their policy to generate clock from external
>sources and PDH can not be used for SDH clock source - that's what
>they said) [For what I read on the interwebs SDH was specially
>designed to support relaying of PDH - so I don't really get the
>point...]

The SDH clock will be country or intercontinental in scope for any
carrier - in our network we will use our caesium clock sources for
stability thank you :)

in reality, 2 different SDH networks would normally be clocked
accurately enough that clock slips between different networks are rare
- maybe less than 1 a year?

>So we receive E1's and STM-1 on different source clocks. 
>Unfortunately Audiocodes tells us the gateway only supports one
>single clock source, which has to be the STM-1 or any external clock
>directly connected to the device.

E1 is "PDH" and the standards allow for 50 ppm clock variation between
the source of any circuir and a notional 2.048 Mbps accurate clock. It
is common practice to use a different clock on each E1, produced by
whatever is plugged into the source port at 1 end (or even different
clocks at each end of the same E1)

However - if you are getting a TDM voice / fax signal within each E1,
the voice signals in the G.732 64k channels have much more stringent
timing constraints, and should all trace back to another "carrier
class" accuracy clock.

1 slip every 20 sec is 1 part in 40m or so and you should get much
better accuracy than that / lower slip rate

Your equipment should use a "voice" clock from 1 or more of the E1s -
but it probably assumes they are all locked to the same clock.

So - your voice / fax stuff is where you want to look

maybe you are getting clock from multiple places and 1 of them is
inconsistent (note "wrong" here is likely to be agrued + vary between
the telcos....)

-- 
Regards

stephen_hope@xyzworld.com - replace xyz with ntl




Date: Fri, 13 Jan 2012 23:13:48 -0500
From: Moderator <telecomdigestmoderator.remove-this@and-this-too.remove.telecom-digest.org>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: LightSquared in 11th-hour effort to woo Washington 
Message-ID: <20120114041348.GA24515@telecom.csail.mit.edu>

By Jasmin Melvin

WASHINGTON | Tue Jan 10, 2012 7:26pm GMT 

WASHINGTON (Reuters) - Telecom startup LightSquared is mounting a
last-ditch effort to win U.S. regulatory approval for a new wireless
network after being outmaneuvered by the GPS industry, which has spun
doomsday scenarios of interference problems that could cause planes to
fall out of the sky and threaten national security.

http://tinyurl.com/824uv4l

-- 
Bill Horne
Moderator




Date: Fri, 13 Jan 2012 23:07:14 -0500
From: Bill Horne <bill@horneQRM.net>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Setback for LightSquared 
Message-ID: <4F10FF72.7090704@horne.net>

The Wall Street Journal

By AMY SCHATZ

WASHINGTON--A government advisory board concluded that start-up
LightSquared's proposed wireless network would significantly interfere
with GPS devices, in a setback for the multibillion-dollar plan.

In a letter Friday to the Commerce Department, the board also said it
saw no quick way to fix the problems.

http://tinyurl.com/7ubqhho

-- 
Bill Horne
339-364-8487




Date: Fri, 13 Jan 2012 23:36:50 -0500
From: Moderator <telecomdigestmoderator.remove-this@and-this-too.remove.telecom-digest.org>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: former Deutsche Telecom Execs charged with bribery by SEC 
Message-ID: <4F110662.8000708@horne.net>

This story is from December 30th, but I haven't seen it mentioned on 
other lists, so I'm publicizing it here.

Written by: Stormy Beach 

The Securities and Exchange Commission (SEC) has charged three former
Deutsche Telekom executives with bribery of government officials. The
charges go back to 2005 and 2006 when government officials in
Macedonia and Montenegro. The reported transfer was about $6.3 million
to Macedonia officials disguised as consulting and marketing
contracts.

SEC also found the same execs in 2005 paid nearly $9.5 million to
third-party consultants in four fake contracts later funneled to
Montenegrin officials. This was pay off for helping Magyar buy Telekom
Crne Gore.

http://tinyurl.com/7n29x7k

-- 
Bill Horne
Moderator




Date: 13 Jan 2012 14:52:02 GMT
From: "Bill Matern of NComm, Inc." <wtm@ncomm.com>
To: telecomdigestmoderator.remove-this@and-this-too.telecom-digest.org.
Subject: Re: Different clock sources for STM-1 and E1 ??

[Crossposted from comp.dcom.telecom.tech - Moderator]

On Mon Jan 9 07:21:42 2012 René Hüftlein wrote:
> Hi!
>
> Maybe someone here can help me with a problem we have with our PSTN
> gateway.
>
> We receive 63 E1's channelized into a STM-1. The E1's are provided by
> DTAG (German PSTN) and are multiplexed into the STM-1 provided by
> Verizon. STM-1 directly terminates in a Audiocodes Mediant 3000 which
> demultiplexes STM-1 and routes E1's respectively.
>
> We see a huge number of Controlled Slips (one in 20 seconds) and it
> seems this condition causes fax calls to crash.

When setting up a system that transports E1s over an STM-1 interface, 
you can use one clock for the STM-1 interface and a different clock for 
the E1 interface. These two clocks should be locked to each other and be 
derived from the same source, but do not have to be which your case is - 
The E1 clock from DTAG and the SDH from Verizon are not locked to each 
other.

The source of your slips is coming from the mis-match of these two clock 
rates.  What is happening is that on your Audiocodes receive side, it is 
receiving the STM-1 and de-multiplexing it into E1s.  The differences in 
frequencies of the STM-1 and the E1 are dealt with [via] pointer 
justifications happening at the TU-12 path level (A TU-12 is what is 
used to transport an E1 over a SDH network - you have 63 TU-12 paths - 
one for each E1).  Since these frequencies are different, if your 
Audiocodes box does performance monitoring, you should be able to look 
for pointer changes at the TU-12 level to see that these two clocks are 
different.

Pointer changes are not the same as slips.  A slip occurs when the 
receive clock on the E1 is different from the system clock in your 
Audiocodes box.  Inside the E1 framer of the Audiocodes box, there is a 
block of memory that the timeslots of the E1 are stored as they arrive 
on the E1 using the receive E1 clock rate.  The timeslots are then 
readout of this block of memory at the system clock rate.  NOTE: This 
block of memory is called the elastic store or slip buffer.   So, what 
happens when the rate of timeslots arriving on the E1 is faster than the 
system takes them out.  Since there is not infinite memory, the E1 
framer will do a controlled slip which would, in this case, would delete 
an entire frames worth of timeslots.  Conversely, if the rate of 
timeslots arriving on the E1 is slower than the speed the system takes 
them out, the E1 framer device will create timeslots by duplicating the 
last frames worth of timeslots.  The deleting/creating timeslots during 
slips will be hardly noticeable to the human ear, but for data services 
like fax, it will cause the kind of problems you are seeing.

So, the solution to you problem is to get the system timing of the Audio 
codes box to be locked to the E1 clock rate.  That may be difficult, if 
not impossible, given the features you describe that are available in 
the Audiocode box.  You indicate that you only have two choices for 
system timing on the Audio codes box:  Receive STM-1 or external input.

Since the STM-1 clock is derived from Verizon's network and the E1 clock 
is from the DTAG network, you cannot use the STM-1 clock because they 
are not locked to each other.

Thus, you need to provide a clock on the external input that is locked 
to the DTAG timing somehow.  You don't have enough description to 
determine if that is a difficult thing to do or not.

Finally, you can find a different receive device that allows the system 
timing to be locked to the receive E1 clock.

Good luck.

Bill Matern
wtm at ncomm.com






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