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From telecom@delta.eecs.nwu.edu Tue Aug 18 00:59:23 1992
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Date: Mon, 17 Aug 1992 23:59:04 -0500
From: TELECOM Moderator <telecom@delta.eecs.nwu.edu>
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To: ptownson@gaak.LCS.MIT.EDU
Subject: computer in hotel
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To: telecom@eecs.nwu.edu
Cc: Charlie.Mingo@p4218.f70.n109.z1.fidonet.org
Subject:
Faxphone: 408-974-0781
Voicephone: 408-974-4535
Date: Mon, 17 Aug 92 16:54:43 -0700
From: malcolm@apple.com
Status: R
Pat, these are two files that give advice on connecting a modem to the
European Phone System. Not being European I don't know the rules over
there but I suspect the local telephone authories will be mighty pissed
if you damage their equipment.
These files come from the IBM PC Forum on Compuserve. Charlie Mingo
downloaded them for me.
Cheers.
Malcolm
P.S. Pat, I've included the original CompuServe file names.....perhaps you
will want to just stick this entire message in a file with a new name and
save the whole thing in the archives.
******* travel.kit *******
20 July 1990
HOW TO CONNECT YOUR COMPUTER TO A HOTEL PHONE
By Paul Munoz-Colman [71141,1224]
Earle Robinson [76004,1762]
Charles Wangersky [73747,2656]
Connie Kageyama [76703,1010]
John Boyd [75076,2466]
Robin Garr [76702,764]
Updated from an idea originally written by
Joan Friedman [76556,3643]
------------
INTRODUCTION
------------
This file describes a method which you can use, and equipment which you can buy
to use your computer and its modem with phone systems which aren't familiar to
you. Telephone systems are very different in appearance and design. There are
wall phones, desk phones, and cordless phones. (For your purposes, with
cordless phones, you deal only with the base station set, not the movable
part.)
There are hard-wired phone lines, all sorts of national phone plugs and jacks,
and modular (small plastic connector) plugs and jacks.
A few simple facts are all you need to make it easy to connect your computer
and become productive.
-------------
BASIC CONCEPT
-------------
The idea of connecting a telephone in a strange location to your computer is as
simple as it is at home. The basic principal is to connect the modem's LINE
jack to the hotel phone's incoming phone line--the wires that feed the
connection to the hotel's instrument.
Most telephone systems have one thing in common: no matter how many wires
connect the telephone to the outside, only TWO are used for the "talk pair", or
what gives you the ability to connect the computer. This concept is very
important: your mission is to determine how to connect to this pair of wires
and stay AWAY from all of the rest of them!
--------------------------------
ELECTRONIC SAFETY MUST BE FIRST!
--------------------------------
First, a little defensive measure! The wires which you use to connect your
modem to the telephone system must have ONLY TWO copper conductors in them. You
can visit Radio Shack (known as Tandy in Europe), or your computer supplier,
and obtain a modular telephone cord like this which has a plug on each end. If
you look at the plug very carefully, you'll notice that it has six little
grooves, on the side of the plug opposite the tab which you press to unplug it.
Some of these grooves are shiny, and some look like plain plastic. The ones
which are shiny have conductors (metal that connects the groove [or pin, as
it's called] to the same groove on the other end). If you hold the cord up to
the light, and if it has a translucent outer cover, you can see two wires
running through the length of it. You will also be able to see the wires in
each of the two plugs, since the plugs are made out of clear plastic. In some
of the cords, if you look closely, you'll see that the center two wires are
colored red and green.
Common home telephone cords have four conductors out of the six grooves; you
only want the MIDDLE TWO to be connected.
Why be defensive? Strange telephone systems may use the other pins for
various purposes, such as signalling a message waiting for you at the hotel
desk. Some computer modems have the conductors other than the talk pair
connected to the phone jack, as well, and strange phone systems can destroy
your modem if the wrong electrical signals appear.
Not only are we worried about only having the talk pair connected to your
modem, we have to worry about stray electrical currents through the phone line
itself, such as the jolts from lightning (which can wipe you RIGHT out)! You
need to have a telephone line surge suppressor that you plug into the hotel's
phone outlet, and your modem's cord into the suppressor. Note that most phone
line surge suppressors also will have to plug into your power strip; the way
the suppressor works, it takes the surge that is coming up the wires to
explode your modem, and instead convinces it to go down the ground wire of
your power strip, where there is nothing that can get hurt by it. This, in
case you hadn't noticed, is a Good Thing.
-------------------------
AHA! A PICTURE, AT LAST!
-------------------------
Now, the connection idea. Here is a simple drawing of what we're trying to
achieve. The idea is to connect your computer to its modem (unless you have a
portable which has it connected internally). If it is external, you then
connect the computer's and the modem's electrical cords to your power strip,
which MUST contain an AC power surge suppressor (not the same as the phone
suppressor). If you are in a country whose electrical supply is 220 volts,
you will need to get a 220V power strip with surge suppressor; 110V surge
suppressors have been known to literally explode when connected to a 220V
power line, and even when connected to the 110-volt end of a 220V to 110V
transformer.
In portables, these two
are generally in the
same casing your phone surge suppressor
/ \ /
|==========| ============ |-| |==========|
| your |-------| your |--------| |----| hotel's |
| computer | RS232 | modem | phone |-| | phone or |
|==========| ============ line | | line |
| | | |==========|
|-----------------------------------------------|
| your AC power strip which is surge-suppressed |
|-----------------------------------------------|
|---------------------------|
| hotel's electrical outlet |
|---------------------------|
-------------------------------------------
AC POWER 1: CONNECTING WITH A CONVERTER KIT
-------------------------------------------
You are, of course, travelling with your AC power bar and surge suppressor.
You should also have a power line polarity checker (polarity means which way
two wires connect to where they're going [there are only two choices,
right?]). If your modem is internal, you have one electrical cord to connect;
if external, you'll have two; many phone line surge suppressors use the ground
pin on a third, so you would have to connect that as well. You should also
have an extension cord in case the hotel's outlet is not convenient to either
you or the phone line; this should probably be the 110-volt variety. The
adapter plugs that come with most converter kits, and the transformers sold in
most converter kits, are *not* grounded; you may have to run a separate wire
from the center screw in the wall outlet in the hotel room, to the wire
attached to your 2-prong to 3-prong adapter. Most foreign power kits come
with two 220V to 110V boxes, a little light one, rated at 1000 watts or more,
called a "Converter", and a heavy one about the same size, rated 50 watts and
called a "Transformer". DO NOT, under any circumstances, plug your computer
or modem into the 1000-watt converter; if you do, you will suddenly have a
room full of smoke and no computer any more.
To hook yourself up to the power line, then, you should do the following:
1) Connect the wire on the 110V 2-prong to 3-prong converter to the screw in
the center of the power outlet. We do this first because it will be harder
to reach this screw after something has been plugged in.
2) If in a location where the use of a transformer is appropriate, plug the
transformer into the wall, with the appropriate connectors.
3) Plug the 2-prong to 3-prong adapter into the converter.
4) Plug the power-line polarity checker into the 2-prong to 3-prong adapter.
If it indicates that the polarity is reversed, unplug the transformer from
the adapter plug, turn it around, and plug it back in.
NOTE: If the polarity checker still says you have reversed polarity, you
are going to have to attach to the phone and power lines without surge
suppression; you might want to send a brief prayer to the patron saint of
communications. Then, disconnect the wire from the center screw of the
power outlet.
5) Unplug the line polarity checker, and plug the power bar or surge
suppressor into the 110V outlet at the end of the whole business.
-------------------------------------------
AC POWER 2: CONNECTING DIRECTLY TO THE WALL
-------------------------------------------
If your modem or computer is rated for the voltage available where you are
located (220 to 240 volts for 220-volt equipment or 110 to 130 volts for
110-volt equipment), you can plug it directly into the hotel's outlet. If in
a 220 to 240-volt area, you will need to get a 240-volt surge suppressor,
preferably in the country where you are travelling; then, plug that into the
wall, and plug your grounded 240V power-strip into that. Most European
countries use a round plug with two round prongs and a metal strip up the side
for ground; the UK is rather vastly different, with a square 3-prong plug.
So, unless your travels are going to cross the UK, you should be all right
with a single type of power bar and surge suppressor.
We have never seen a phone-line surge suppressor in Europe; no doubt they will
be following hot on the heels of deregulation, but for the moment, you have to
put your trust in the PTT.
--------------------------------
AC POWER 3: WHAT USUALLY HAPPENS
--------------------------------
Usually, a 220-volt-equipped computer takes too much power for the little
50-watt transformer; or, the computer plus the modem sum to more than 50
watts, but the computer's battery charger draws less than 50 watts. What you
do then is run the computer off 220V, or off its internal batteries; and the
modem off the transformer. You will still need to connect the power strip, or
the surge suppressor, as mentioned in AC Power 1, in order to get the phone
line surge suppressor to work.
------------------------------
DIFFERENT TYPES OF PHONE CORDS
------------------------------
Not only should you obtain a modular telephone cord with only two conductors
in it, but you should also obtain one with a modular plug on one end, and what
are called "spade lugs" on the other (metal U-shaped connectors which can slip
under the head of a screw, which is then tightened down to make an electrical
contact of metal to metal).
---------------
RJ-14 THREE-TAP
---------------
At Tandy/Radio Shack, you can buy what's called an RJ-14 three-tap connector.
One end of this plugs into a modular phone jack which can be either one-line
or two-line capable. The other end has an identical RJ-14 outlet, and two
other RJ-11 outlets, one stenciled with LINE 1, and the other with LINE 2.
(VERY IMPORTANT: You aren't going to use LINE 2 at all for this purpose.)
-------------------------------------------------
MODULAR, RJ-11, RJ-14: WHAT DOES THIS STUFF MEAN?
-------------------------------------------------
Well, it's like this. Before the "breakup", Ma Bell (actually Western
Electric) invented this new, neat system to connect phones to the wall, and to
connect phones together; you can replace bits of the phone that are most
likely to break, namely the wires, without having to open the case of the
phone. Just plug in a new wire.
Because you can repair a phone simply by replacing the specific modules that
make it up, the whole system became known as "modular connectors". These come
in a number of sizes: two, four, six, up to twelve connectors; and they are
extremely rugged, as anything attached to a telephone is, so a lot of other
people started using them for things totally unconnected with the phone
company. Many manufacturers now use a modular jack to connect the keyboard to
its PPC series of computer.
However, the electronics industry couldn't be satisfied with just calling it
"modular"; they have a different name for each type of hookup. The name, as
is typical of such interface standards, is a series of letters and numbers.
The three types that we will be most interested in are the RJ-11, RJ-12, and
RJ-14.
Most home lines, and most modems, are connected to RJ-11 phone lines. This is
a six-connector jack, with only two pins actually used.
An RJ-12 connector is the exact same size and shape, except that it has four
wires used instead of two. The two extra wires are used by some phone systems
to indicate that a line is in use. You don't have to worry about that; your
modem won't.
An RJ-14 connector uses four wires also, but instead of using the extra two
wires to signal that a line is in use, it uses them to put a second phone line
on the same cable. The center two wires are the main phone line, and the outer
two are the second. (Actually, many US home phone systems are equipped with
RJ-14 modular cords even though the hookup is RJ-11 (two wires), just in case
you decide to add a second line, making hookup easier for the installer. The
center two wires are the main or first phone line, and the next outer two are
the second.)
--------------------
NATIONAL PHONE PLUGS
--------------------
In every country, the national standard for the phone plug is different; so,
you will need to stop by an electronics parts store to buy a PTT-to-RJ-11
adapter in each country you visit. Normally, this adapter plug will be the
local currency equivalent of $3 to $10. In most countries, you can find this
adapter in virtually any electronics parts store.
In London, most of the electronics parts stores cluster in the Tottenham Court
Road.
In Paris, the place to look is the BHV.
In Den Haag (the Hague) in the Netherlands, there are a number of stores
around the Pavilioensgracht, though the best store we've found is Stuurt en
Bruin at Prinsegracht 34. You can also buy the adapter plug at any Primafoon
outlet in the Netherlands; addresses for Primafoon will be in the very
beginning of the white pages section of the phone book. (Look for a page
printed in green.)
And, nowadays, in the U.S., most hotels and motels use the modular connector
almost exclusively.
--------------------------
OLD-STYLE FOUR-PRONG PLUGS
--------------------------
You may also need a special converter which has a modular phone jack on one
end and a four-prong phone plug on the other; Radio Shack has these.
-----------
OTHER TOOLS
-----------
Last in your kit, have a flat-blade screwdriver (1/4 inch is required, and 1/8
inch is convenient), and a phillips screwdriver (#1 is the most common size).
--------------------------
MOVING RIGHT ALONG, NOW!
--------------------------
------------------------
PHONES WITH MODEM JACKS!
------------------------
Nirvana! The easiest hookup is going to be in the very modern hotels, which
have telephones that contain a modem plug; when you encounter this, you laugh
a lot, first! Plug your two-conductor modular cord into the phone jack, and
the other end into modem, just as if you were at home! Put me away, you need
read no more! Dial CompuServe and get your latest stock quotes!
------------------------------
PHONES WITH MODULAR WALL JACKS
------------------------------
The next best hookup is a hotel where the telephone is connected to the wall
with a modular plug. (Sometimes the modular plug is hidden behind a wall
plate that you must unscrew first.) When you unclip the modular plug from the
wall, plug your RJ-14 3-splitter into the wall. Plug the HOTEL's phone back
into the tap marked RJ-14. Plug YOUR two-conductor modular cord into the tap
marked LINE 1, and again, read no farther!
-------------------------------
PHONES WITH FOUR-PRONG PLUGS
-------------------------------
If you find a phone with an old-style four-prong plug, unplug the phone, plug
in your modular-to-four-prong converter, plug your modular extension cord into
the wall, and go to it!
--------------------------
PHONES WITH NATIONAL PLUGS
--------------------------
If you find a phone with a national plug, unplug the phone, plug in your
PTT-to-RJ-11 converter, plug your modular extension cord into the concverter,
and go to it!
----------------------------------
PHONES WITH A SQUARE CONNECTOR BOX
----------------------------------
Now it gets a little more difficult. You walk in and find a phone with a cord
that goes into a little square box at the base of the wall. There are two
kinds of these boxes, the kind with only a single screw in the cover, and the
kind with no screws at all.
If the box has a single screw in the center, take your 1/4 inch flat-blade
screwdriver, and gently unscrew the screw.
If there are no screws on the box at all, look around the top and sides of the
box for a little slot, the right size to take your 1/4 inch screwdriver; when
you find it, insert the screwdriver and gently twist it. The box will pop
open on a hinge. (Note: this type of phone box is used especially in new
construction in Canada.)
You'll usually see three or four screws below the cover. Each screw will have
one or more wires secured under it. The wires attached to the screws are
usually color-coded, though the colors will be different for each country.
In a lot of countries, they will have letter codes; two of the wires will be
labelled something similar, like L1 and L2, or A and B, or if you are really
lucky, "Tip" and "Ring".
If there are lots of wires behind the wall plate, like 25 or 50, there will
probably be also a lot of wires labelled the same way, "L1" and "L2", for
instance. In this case, look only at the wires which are also connected to
your phone. The other ones will be connected to other telephones in the hotel,
and if you start playing with them, the hotel will be very mad at you.
Carefully loosen one screw slightly, touching *only* that screw with your
hands and the screw driver (if you touch the two screws that go to your phone
at the same time and the phone happens to ring, you'll get a truly unpleasant
jolt). Take your modular cord with the spade lugs, and slip one spade lug
under it (don't let any other spade lugs slip out), and gently tighten the
screw back down. Repeat the process for the other screw.
If the screws are close together, be SURE not to let the metal from one spade
lug TOUCH the metal from the other one!
Crank up and compute!
------------------------------------------------------
PHONES THAT CAN'T BE OPENED OR WITH INACCESSIBLE WIRES
------------------------------------------------------
There's an alternative connecting device which can be obtained which will
hook up phones where the *only* thing you can get to is the modular cord which
clips into the mouthpiece. This isn't cheap, however, because of the
electronics which are required to make this connection safely and correctly.
See the description of the Konexx unit at the end of this kit.
---------------------------------------------------------
PHONES WITH DISAPPEARING WIRES AND WALL PHONES (ARGGHHH!)
---------------------------------------------------------
If you are lucky to find a wall phone that is plugged into a modular plate,
you can push up FIRMLY on the bottom of the phone, which will move it up about
half an inch (don't be surprised if you hear a snap when this happens), and
remove it from the wall; plug in your modular cord (if you want to use the
phone ALSO, don't remove it, just tap into it as follows).
Sigh!
All the easy solutions are gone now, but have no fear ... we'll get there. You
find no modular or national plugs, and no little box in the wall ... the wire
just disappears in there. So we tackle the telephone instead, to find those
little two wires.
Turn the phone over and find the screws which undo the case. If you have a
conventional desk set, the screws are on the bottom. If you have a wall
phone, the screws are under the "number card" plastic protector (you can pop
this out with your 1/8 inch screwdriver blade). Take the case off the phone.
Find the place where the phone wires connect to the phone line. In some
countries, notably the Netherlands, this is under a plate on the bottom of the
phone which is held on by only one screw; this is all neatly labelled as well.
Follow the two wires you are looking for to the screws that hold them down.
Very often, this place appears on a plastic-looking wire block with many
screws. The two you need generally have something like "L1" and "L2" or "a"
and "b" stenciled next to the screws with the correct wires. DON'T touch any
other wires on this block!
Perform the process where you loosen the screw and hook your spade lugs into
them, and tighten down, one at a time.
Finally, take a break, relax, read the paper, take a swim, and compute at your
leisure ... YOU EARNED IT!
-------------------------------
COLOR CODING: HOW'S THAT AGAIN?
-------------------------------
Every country has its own standards for coding the telephone lines; these
usually depend on the colors of the wires, which means that you can't work
for the phone company if you are color blind...
For historical reasons, the two wires that make up your phone connection are
called "tip" and "ring". In the old days of the manual switchboard, each
phone line was connected to a single plug at the switchboard, which looked
very much like a large (1/4") stereo headphones plug. One line, the line that
was at the lower (and therefore safer to touch) voltage, was connected to the
connector at the tip of this plug, the other was connected to the ring around
the end of it, and the sleeve, or the rest of the plug, was connected to
ground.
In the United States and Canada, the tip connection is always on the green
wire, the ring was always red. Sleeve was yellow, for some reason, but that
wire was usually not connected, so the name "sleeve" for that wire didn't
become popular.
These days, the polarity of the phone wire doesn't matter as much; as recently
as 1980, a phone line had one polarity if it was a dial line, another if it
was a touch-tone line. Before the introduction of touch-tones, all phone lines
were supposed to have the same polarity. So many places will have tip and ring
reversed. To the best of our knowledge, no modem sold for personal cares
about whether tip and ring were reversed.
Every country has its own color coding for the wires, as we said earlier; the
following table, while still incomplete, will list the colors used for the
two wires that your modem *must* have in order to work. Where two colors are
listed in one column, this means that the main color of the wire is the first
color, and it has a stripe of the second color; so "blue-white" is a blue
wire with a white stripe. If you discover errors in the table, or want to
add a new country to the list, please post a message for SysOp in IBMCOM, or
in IBMEUR, or contact Charles Wangersky [73747,2656].
For what it's worth, if you wish, you can use a voltmeter instead of a line
tester. Some people (like us) travel with a voltmeter. In this case, you can
tell tip and ring on your phone line by checking for a 48-volt signal when the
phone is hung up or disconnected; the ring line will be at -48 volts from the
tip line. The tip line will be near ground potential; the way to tell the
difference between that and sleeve is to pick up the phone. The sleeve voltage
won't change, but the voltage on the tip line will go from about 0 to about -2
volts; meanwhile the voltage on the ring line will drop to about -10 volts.
Country | Tip (+) | Ring (-)
---------------------|-------------|-------------
USA/Canada (normal) | Green | Red
USA/Canada (special) | Blue-White | White-Blue
Netherlands | Red | Blue
Germany | Red-black | Red
United Kingdom | White | Blue
----------------------------------------------------------
SPECIAL NOTE FOR PEOPLE TRAVELLING IN THE UK AND HONG KONG
----------------------------------------------------------
The United Kingdom and Hong Kong use a different make/break ratio in their
phone dialers; a dial pulse in the UK is 33% of the time between one pulse
and the next, where in the US it is 39%. This doesn't sound like a big
difference, but it is; if you try to use the US pulse ratio on a UK phone
line, it will not work.
Luckily, the people at Hayes who invented the standard for personal
direct-connect modems were aware of this difference, and so, starting with the
Smartmodem 1200 internal, included a command to change the make-break ratio;
and so nearly all other modems today have the ability to change from one to
the other. The command to set the UK pulse ratio is &P1; to reset it to US
standard, &P0.
So, to change to the UK standard, you could send the command "AT&P1&W" to your
modem; this will change its power up default to the UK system.
----------------------------------------------------
YOU MUST HEED THIS WARNING FOR YOUR OWN PROTECTION!!
----------------------------------------------------
Under no circumstances use ANY other wires inside the phone instrument or the
wall connector to connect to your modem. If you do so, you can destroy the
electronics inside the modem, inside the phone, and in some bizarre cases,
even inside your computer.
ONLY the L1 and L2 incoming wires have the proper electrical signals to give
to your modem's telephone line (the right combination of voltage, current,
signals, and other characteristics)! Under no circumstances use a connection
cord to your modem which has more than TWO conductors in it!
If the phone rings while you are connecting wires to it, or if you are
connecting wires while the phone is picked up, IT CAN BITE YOU! The voltage
used to ring the bells in the phone is 150 volts, 25 Hz; in the UK, it's 250V
at 25 Hz. This HURTS! If you have a weak heart, it can kill you! In many
countries, there is a meter on the phone; to make the meter tick over, the
phone company puts a pretty stiff voltage down the same wires that you will be
connecting to; in the Netherlands, this is 100 volts at 25 Hz. This also
hurts. When working with live circuits, remember this rule: ONLY ONE HAND ON
ANY PIECE OF EXPOSED METAL OF ANY KIND! EVER!
-------------------
YOUR PHONE KIT LIST
-------------------
All of this, except for the surge suppressor and the mouthpiece interface, can
be acquired for about $50 at Tandy/Radio Shack or a local hardware store.
The phone line surge suppressor is a Networx Wire Cube, and can be had for
about $30.
The kit should contain the following:
2 TWO-conductor modular-to-modular phone cords, each 25 feet long
If you can't find 25-foot long two-conductor cords, you
must have at LEAST one TWO-conductor cord of ANY length
used (you can combine this with FOUR-conductor cords with
your in-line connector).
1 in-line modular phone connector (hard plastic about 2" long)
1 3-jack RJ-14 to RJ-14 / RJ-11 / RJ-11 modular phone converter
1 TWO-conductor phone cord with modular connector on one end,
and two spade lug connectors on the other. If you can't find
a TWO conductor cord, buy a four conductor cord, and CUT the
spade lugs off of the yellow and black wires and throw them
away!
1/8" flat-blade screwdriver
1/4" flat-blade screwdriver
#1 phillips screwdriver
2-prong with strap to 3-prong electric plug tap
Power-line adapter kit
Power-line surge suppressor (either separate or built into power bar)
Power-line polarity checker
Heavy-duty three-prong electrical extension cord
Utility knife
--------------------------------------
OPTIONAL EXTRA ITEMS FOR THE PHONE KIT
--------------------------------------
One of the most useful things that you can get is the little AT&T or Radio
Shack phone line tester; this will plug into the RJ-11 jack and tell you
whether you've gotten it wired correctly. It can also detect whether you have
a single- or dual-line phone, if you find a modular jack already installed.
This gizmo is only available in North America; since modular jacks aren't very
popular as yet in Europe, the Tandy stores over here don't see any point in
carrying them. If you're already in Europe, and you need such a tester,
contact Earle Robinson [76004,1762]; he has kindly offered to provide these at
his cost to the first dozen (or so, depending on how many he picks up) people
who contact him after each of his trips to the States.
The mouthpiece interface is a Konexx unit, from Unlimited Systems Corp, Inc,
9225 Chesapeake Drive, Suite J, San Diego, CA 92123. Two models are
available. The 106 will work for most modems ($99), and the 107 ($125) will
support the few modems that require it and fax machines. The unit is about
2" x 1" x 1", and plugs into the telephone base unit where the hand set cord
goes. The hand set then plugs into one end of the unit, and your modem into
the other end. A switch changes from Voice to Data transmission.
---------------------------------
A WORD OF CAUTION ON THE TOOL KIT
---------------------------------
It's useful to realize that the tool kit, with its suspicious looking wires and
tiny tools, could likely attract the attention of the inspectors at airline
security checks. A smile and a reasonably good attitude are definitely the way
to go when they start pulling your suitcase apart and looking at you strangely!
---
END
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******* phones.deutschland ********
Installing a modem in Germany can be a very time-consuming job. The PTT comes
with two wires (named a and b, b=Ground), but then there are several
different possibilities. This notice here gives some hints.
First you must know, that the german PTT has a different concept. If you have
more than one device on one telephone line, and one is active, all other must
be dead. The PTT tries to garantie privacy. This concept leads to the fact,
that if you have devices in parallel (this is forbidden), and one device is
dialing, the other will ring or detect a ring. The privacy concept depends
therefore on special switching facilities build into the telephones.
Old style connector:
VDO4 Connector:
4 3 2 1 a and b the telephone wires
| | | | E means the local Ground (Earth)
E W b a W is the Bell (German: Wecker)
The normal telephone connects a and W, if the handset on the telephone. (It
drives a second bell, perhaps). If you pick up the handset the connection of
a-W is opened.
VDO7 Connector:
7 6 5 4 3 2 1
| | | | | | |
G E W b a b' a'
This connector is used at the main-device, if two devices are connected
to the line. a' and b' are driven from the connected device and go to
the second telephone. But the same connector VDO7 is used, when a modem or
automatic answering system is installed. In this case the ADO8 connector is
the first connector.
ADO8 for Modems:
a --- 1 8 --- a'
E --- 2 7 --- W
G --- 3 6 --- Z
b --- 4 5 --- b'
If the ADO8 Plug is not inserted, two internal switchec connect a with a' and
b with b'. So if you want to connect somthing to the telephone line, you can
simply use the pins 1 and 4 of the ADO8. But if you want to use the telephone
behind properly, certain connection have to be made, depending on the type of
equipment, that is installed.
Sometimes you find ADO4 Connectors:
a --- 1 8
2 7 --- W
3 6
b --- 4 5 --- E
The ADO4 has also two internal switches for a and b. But the other sides of
the switches are connected to internal screws.
New connectors TAE6:
The connector type TAE is available from TAE6 to TAE16, depending on the
pin count. Mostly TAE6 is used. In the future it is planned to use the modular
jack adapter called "western"-connectors from german PTT. But at this time
TAE6 is installed for new lines.
1 2 3 4 5 6
| | | | | |
| | +- G E -+ | |
| +----- b b'-----+ |
+--------- a a'---------+
The logic is just the same as with the above ones. The TAE6 connects a with a'
and b with b', if the plug is not inserted. But like the ADO8 the TAE6 can be
coded as N (normal) and F (TeleFon). A modem is connected to the N-coded TAE6.
But the coding can be overwritten, if you use a bit more energy when inserting
the plug (The other possibility is to cut the coding with a knife from the
plug).
Now, if you have a jack adapter, what can be done?
First, there are smome converters available. They are available from ADO8 to
TAE6 (working with all equipment modems/answering machines). And there are
converting adapters from TAE6 to Jack (RJ11). Normally they do garantee to
give you access to a and b, but they do not garantee that the other equipment
is working well.
(With the Worlport Modem series, we sell Cables one side Jack, other side
TAE6, coded as F or N, and direct connection between a and a'and b and b'.)
The best is, to bring along a modem plus thelephone. And if you find a and b,
all will work fine, but make shure, that you use the CCITT-Make/Brake ratio
for dialing. Otherwise you will often get a connection to a wrong number.
Additonally there is another barrier. Some, especially the older systems, need
a special switch to let you access the PTT lines, when you are connected to an
inhouse system. This is done by connecting E with a. If you need such a
switch, only approved modems will offer it. The corresponding Hayes command is
">" or ":", depending if the modem goes offhook before or after the modem goes
online.
I'm sorry, there is no simple rule how to get online with a modem. It
mostly make sense to travel with a screw-driver and clips. Or to use cups.
(We can supply you with the Tandy-Cups for the Worldport Modem series, as we
are Tandy dealers (send EMAIL). Please note, that the European Tandy-Cups are
different from those in the US. Most European ones, with a PTT sign are not
able to operate at 1200 Baud. Therfore we sell the US-Originals, which even
sometimes work with 2400 Baud).
I know that this text is not complete. There are special switching units
called AWADO1 and AWADO3. They allow to use two devices on the same line. But
instead of simply using the lines a and b, they need the W signal from the
telephone device to work properly. And the german PTT uses several different
diagramms. Often int is not easy to find out, what sort of diagramm was used
and why. But I hope that you are now able to find a and b on all sorts
of connectors! If you need a special advice, send EMAIL.
RzK D.Kpke, Bitzenstrasse 11, D-5464 Asbach Ww., FAX 49 2683 4537
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