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1997-05-30
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Sun, 25 May 1997 13:38:01 comp.dcom.modems Thread 177 of 256
Lines 195 Re: USR X2 Modems . Do they Work??? Or just 1 Response
wizard@dont.bother.responding.com Wizard at The Wizard
I use two USR x-2 externals. I connect to a 56K connection through
ioNET. My DCE connections are consistently 53.3 and 54.6K.
If you rarely get 53.3 kbps or 54.6 connects, (current Federal Regs do
not allow for true 56K connections) the reason is almost always a
result of phone line quality. 56K modems are pushing the limits of
today's telephone system. Getting 56K bps connections requires
pristine telephone line conditions end-to-end. The following three
paragraphs, which are from a paper entitled Of Line noise, The Phone
Company, and Your Modem by Patrick Moore, Supra Corp., explain this in
more detail:
- Repeatable results with V.FC/V.34 modems on real-world phone
lines are sometimes difficult to obtain. Unlike V32.bis modems,
V.FC/V.34 modems will actually modify their data coding (symbol
rate) and transmit levels during the connect phase. Very minor
differences in the phone line can lead to different results.
- A 28.8K connection on some real-world lines may not occur very
often, if it occurs at all. Preliminary testing in the lab
indicates that "normal" phone line attenuation makes a 28.8K
connection difficult even in the absence of line noise. This is
not surprising considering that the V.FC & V.34 coding schemes
rely on the bandwidth of the phone system being greater than
what is actually available in some areas. Very high-speed
connections assume that there is a substantial amount of digital
technology in the system (thereby normally increasing the usable
bandwidth). Some users are going to find that their local phone
system effectively limits them to 16.8K or 19.2K.
- Both the originating and the answering modem are adjusting to
their line conditions during the connect phase. The fact that
a connection to a given modem at a given location occurs at a
lower rate (19.2k for example) may have nothing to do with the
modem the call is placed with, or the location it is placed from,
as the modem on the other end may be adjusting the baud rate
down.
For the above reasons, many people will never see 53.3K or even 54.6
CONNECTS with their 28.8 modem. The easiest way to find out if its
your phone line or your modem is to find someone who usually gets 53.3
or 54.6 connects, and try your modem on his system, or his modem on
your system. You will most likely find that the problem at your end is
phone-line related.
The part of the telephone system which you may be most able to improve
is your telephone premises wiring. If you rarely get 53.3 or 54.6
connects, try the following:
Premises Wiring . . . Often faulty premises wiring, bad phone jacks
and plugs, cheap phones, old/antique phones, or too many phones or
other devices cause problems. Here is how to determine if your
premises wiring or equipment is affecting your CONNECT quality. Find
the telco wiring block where all your premises wiring connects -- it
will usually be outside or inside of your house near where the phone
line comes in. Look at the interior wiring. The best wiring is
"twisted pair". Most older, non-twisted pair wiring consists of four
wires in a single jacket. The individual wires have solid color
insulation (green, red, yellow and black -- but only the green and red
wires are normally used on a single-line system). Twisted pair wiring
consists of matched pairs of wires, normally 2 or 3 pairs in a single
jacket. The two wires in each pair are twisted around each other in a
gentle spiral. Of each pair, one wire has a colored insulation with a
white stripe, and its mate is white with a matching colored stripe
(i.e. white with blue stripe and blue with white stripe).
If you have non-twisted pair wiring, you should consider replacing it.
But whether you have twisted pair or not, you may want to try this
experiment. Run a good quality twisted pair phone cable directly
between the block and the phone jack that serves your modem, routing
so as to avoid other electrical wiring and devices -- and then
disconnect all other premises wiring from the telco block. If this
gives you faster connects, then your premises wiring or your phone
equipment is causing you trouble. Reconnect wiring and phone devices
incrementally while retrying the modem to see if you can find the
culprit. Examine each plug and jack, and reseat each several times.
Where visible, inspect the routing of the phone wiring to assure it
steers clear of other wiring and electrical devices. If you find some
of your equipment or premises wiring is contributing to the problem,
the recommended solution is to replace or eliminate the equipment
and/or wiring. However, read on for one alternative solution.
Using a "Teleprotector" . . . There is one other solution that I have
used to eliminate premises problems without replacing or eliminating
premises wiring or equipment. I have an antique pay phone which was
causing a problem, but I did not want to eliminate that treasure from
my system. I ran a new, dedicated line from the telco block to my
modem jack. Then I bought a $10 device from Radio Shack called a
"Teleprotector" (Cat. No. 43-107). The Teleprotector is designed to
protect fax and data transmissions from interruptions, and to shut-off
answering machines when you lift an extension. The device is a small
cube with a phone jack on one side and a short phone cord with phone
plug coming out of the other side. When installed in a phone line, the
Teleprotector disconnects the phone line downstream of itself when any
upstream device is off-hook.
Here is how I used the device: I marked the cord side of the cube
"telco" and the jack side "phones". I inserted the plug-end of the
line coming out of the Teleprotector into the jack on the other side
of the Teleprotector. Then I cut the resulting cord loop in half, and
stripped the red and green wires at the cut ends -- this resulted in
the Teleprotector having stripped red and green wires sticking out
both sides (ignore the Teleprotector's yellow and black wires). Next,
I removed all premises wiring from the telco block except for the new
line going to my modem. I connected the Teleprotector's red and green
wires on the side marked "telco" to the telco block, and connected the
red and green wires coming out the other side to all of the premises
wiring I had disconnected. NOTE: As mentioned above, most residential
phone systems which use non-twisted pair wire only use the green and
red wires -- you can ignore the black and yellow wires (just leave
them unconnected). Here is a schematic:
Telco Block
Incoming +-----+ Radio Shack
Telco >============o-o | "Teleprotector"
Line | | +---+
| o-o=========| |=======> To all premises
+--\\-+ +---+ phone devices
\\ except modem
\\
``==================> Dedicated line
to modem
DONE! Now, whenever my modem has the line, all other phone wiring and
devices in the house are switched off-line by the Teleprotector. My
average connect rate used to be 24 kbps -- now it is extremely rare
that I get a less-than a 28.8 kbps CONNECT. Another benefit -- now all
of the other phones in the house are dead whenever my modem has the
line, so if anyone lifts a phone it doesn't mess up my data
connection. Lots of benefits from a $10 expenditure!
Telephone Co. Line Quality . . . If you determine that your premises
wiring is not causing problems, and you still get low connect speeds,
you can try a few other things like calling a known quiet number and
listening carefully -- if you hear hissing, humming, a radio station
or other background voices, you have a line problem (you may have a
line problem even if the line sounds quiet). Reporting noisy
conditions will probably be sufficient to get the phone company to
look into the "problem". You may be able to get them to test and
improve your line, but be aware that all they guarantee to provide is
a line meeting voice quality standards, and also they may want to
charge you for the testing if they find no line problem. So you
telling them your modem can't get high speed modem connections
probably won't motivate them. However, it has been reported that the
phone company will generally be responsive to fax problems, so report
those if you have them. Your connect speeds will frequently be lower
when you are distant from your telephone exchange, and when your call
must pass through more than one exchange.