Re: [RT] GEN: TRADING LINES: T-1 & DSL

["Ray Raffurty" <r.raffurty@xxxxxxxx>]

Hi Chas,
 
I work in the telecom industry to support my 
trading, and vice versa {;-)
 
Here is the scoop on T-1 lines.  A T-1 line is 
a twisted pair of copper wires just like a regular telephone line.  
However,  a regular telephone line, which carries analog signals 
(voice), has an amplifier installed every 15,000 to 18,000 feet called 
a "Load Coil".  The problem with these is that in addition to amplifying 
the signal (your voice) they also amplify the noise, making them useless for 
data.  Currently the maximum data rate approved by the FCC for such lines 
is 50,000 (50k) bits per second.  This is the maximum speed of a typical 
56k modem.  However it is nearly impossible to achieve this rate due to 
noise on the line, etc. so the modem will automatically slow down until it finds 
a good rate (48k bps would be considered good).   Note that a 
modem that supports V.42 bis compresses data up to 4 to 1 for a thru put of up 
to 200,000 bps but require a dual UART interface to the PC or a special 
accelerator board.
 
A DSL (Digital Subscriber Line) provides user 
access at speeds up to 128,000 bps depending on line conditions.  A phone 
company technician will need to remove any filters, usually located in the box 
on the outside of your building, and replace them with individual filters on 
each phone in your house/office.  The computer is connected to the line by 
an ADSL Router, often a Cisco 675.  The Load Coils are NOT removed 
from the line, thus limiting the distance that you can be from the phone 
company's switch to about 18,000 ft.  The DSL line has 3 channels, one of 
which is reserved for telephone company signaling, so you can have both computer 
data and voice signals traveling over the same line at the same time (though you 
may notice a reduction in volume of the voice signals).  Each channel 
carries signals at the rate of 64,000 bps.
 
A T-1 line can carry up to 1.544 Mbps (Million bits 
per second).  This is divided into 24 channels, 23 available to the user 
and 1 reserved for signaling, each capable of carrying 64,000 bps.  This 
means that you could have 23 telephone conversations or 23 computer connections 
(or a combination of both) at the same time over the same telephone line.  
This is primarily used by large organizations such as catalog call centers, 
large offices, and large hotels.
 
This is accomplished by first digitizing the analog 
voice signals. A modem converts digital signals (1's and 0's) into analog 
(beeps) and back again, so a digitizer is sort of the opposite of a 
modem, converting voice to digits and back.  The second step is to 
"multiplex" these signals.  This means carrying multiple signals over the 
same line.  There are many ways to do this but the most common is 
"Frequency Multiplexing".  The standard analog telephone can recognize 
frequencies from 300 Hz. to 3300 Hz.  This is not exactly "high fidelity" 
but is adequate to understand speech and recognize another person's voice.  
Thus, a standard telephone line has a "Bandwidth" of 3000 Hz.. 
(3300-300=3000).  You always wanted to know what bandwidth was, didn't 
you?  A digital 1 or 0 does not require this 
much bandwidth.  They only require a bandwidth of 100 Hz, if you 
divide 3000 Hz. by 24 channels you come up with 125 Hz. per channel, more than 
adequate when you separate the 100 Hz. channels by 25 Hz in frequency to prevent 
cross talk. I.E the first digital signal would be carried at a frequency between 
300 Hz and 400 Hz. separated by an empty 25 Hz. so the next signal would travel 
between 425 Hz. and 525 Hz. then 550 to 650 Hz. and so 
on.
 
Because of this the signal cannot travel more than 
1 1/2 miles before the signal is lost, therefore a device called a "Pulse 
Regenerator" (just a repeater) is installed on the line every 6000 
ft.   It looks at the 1's and 0's coming in and send out the same 
signal so that there is no loss of strength.  When you lease a T-1 line you 
pay a "Local Loop" charge which is the charge to provide this special line and 
start at $200.00 per month and go up depending on the distance from your 
location to the carriers point of presence (POP).  There are also 
installation charges but many companies will wave then in today's competive 
market.  You will still pay for long distance call per minuet but it should 
be around $0.04 per min.  Note T-1's CAN NOT carry local calls so you will 
still need a local phone line(s).  You can purchase a fraction of a T-1 
(half or quarter).
 
To use this bandwidth you would start with a server 
connecter to a computer network thru a router.  When one terminal was 
in use it would receive all the bandwidth, then as more and more terminals where 
used the bandwidth would be divided between them.  Depending on your phone 
requirements part of the T-1 could be split off the serve 
them.
 
So what are you going to do with this, start your 
own brokerage firm?
 
If you would like a quote on T-1 service send me 
your area code and exchange (the first 6 digits of your phone number) and I will 
get it for you.
 
Good luck and good trading,
 
Ray Raffurty
 
 
 
 
----- Original Message ----- 
<BLOCKQUOTE 
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV 
  style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black">From: 
  charles meyer 
  
  To: <A title=realtraders@xxxxxxxxxxxxxxx 
  href="mailto:realtraders@xxxxxxxxxxxxxxx";>REAL TRADERS 
  Sent: Tuesday, July 02, 2002 3:41 
PM
  Subject: [RT] GEN: TRADING LINES: T-1 
  & DSL
  Group-Would anyone care to tap out a few comments 
  on the technical difference?I was told that a T1 line is just a 1.544 MB 
  line.  (Not sure what thosenumbers mean though<g>)I'm 
  told that if the other end as a 300 baud moden; its still 300 
  baud,etc...Does my confusion make any 
  sense?<g>chasTo 
  unsubscribe from this group, send an email 
  to:realtraders-unsubscribe@xxxxxxxxxxxxxxxYour 
  use of Yahoo! Groups is subject to the <A 
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