How to Connect Your Computer to a Hotel Phone

How to Connect Your Computer to a Hotel Phone

20 July 1990
                  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]

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.

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!

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.

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 |

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.

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.

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.

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).

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.)

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.)

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.

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.

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!

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!

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!

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!

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!

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!

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.

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).


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!

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

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.

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!

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

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.

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!


Editor: Ali B. Ali-Dinar
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