If anything in here isn't clear or if you have something to add, email me.

If you're experienced with cellular modems, I'd love to hear your opinion of them.

Let me know if this have been useful to you, just because.

The Internet From Payphones

There doesn't seem to be much information available about connecting to the internet through payphones using what's called an acoustic coupler, so here goes my 1.7 cents.  I should say that this is just my experience using one of these things, definitely nothing definitive or anything like that.  If you disagree with anything or have something to add, email me and I'll put it in here. 

I use an acoustic coupler because when I'm on the road it's a little awkward asking someone to use not only their phone, but their wall jack.  Even if I explain that I'm just calling an 800 number, people are still leery, if only because it's such an unusual request.  There's also the possibility of the cellular modem, but cellular coverage is still spotty, especially in the sort of rural areas that I find myself in on roadtrips, and it's expensive.  Hence an acoustic coupler, a device that lets you use certain payphones for your internetting.  It connects right to the modem in your laptop computer. It's my little umbilical chord out the sidedoor of my van connecting me to the Mother Ship Internet. 

It has been my experience that there are no clear rules to using an acoustic coupler, especially when the variable of the payphone is introduced. It's more a delicate art than a science, and if you're going to do it you will succeed in connecting to the internet through a payphone, but not without some befuddling problems along the way.

The basic concepts: An acoustic coupler is an interface between your computer/modem and a payphone. It straps directly to the handset of any phone (it couples) and then plugs into your modem like any other phone line.   You can use it with any modem.  On the coupler are a speaker and a microphone. The speaker goes over the handset's mouthpiece and the microphone goes over the handset's "ear piece". It's like the modems of yore, if your computer experience and/or memory go back that far.   It's hard to describe, so here's a picture of mine:

coupler3.jpg (96266 bytes)coupler2.jpg (97320 bytes)

Click it to see the pic full sized.

My ISP (Earthlink) has two 800 dialup numbers, so I don't have to deal with heavy phone card charges or with pumping in quarters. Earthlink charges me $5/hour for this on top of my regular $20/month ISP fee. I think that's cheap. Checking email usually takes under 5 minutes, which costs me less than fifty cents.  If you're looking for an ISP with an 800 number, I can definitely recommend Earthlink.

The coupler I use -- and the only one I have had any experience with -- is made by a company named Konexx and the model is called the "Acoustic Koupler". It cost me $120.  I got it over the web from a company called "Mobile Planet".  There are other couplers on the market but this one seemed to be the usenet favorite in all three postings I could find that even mentioned acoustic couplers.

Most of the people using acoustic couplers are business types. I'm not a business type: I use my coupler from my van and I have tons of phone wire so I can connect to just about any payphone that I can see. Inside my van I have my laptop, which I power from my car battery using a DC/AC inverter.  I can setup next to just about any payphone anywhere and connect to the internet.

coupler1.jpg (108506 bytes)

Uplinking from one of those steep hills in San Francisco

In the manual for the coupler it says I shouldn't expect better than 2400 baud from most payphones as they tend to use cheap carbon microphones, but I haven't found that to be the case. My typical connection speed is almost always right around 20,000 baud. That is, if I can connect.

Ability to connect to a given phone is the real issue when using acoustic couplers with payphones: many payphones are just too damn cheap to couple with at any speed. I've found that the "name brand" phones (eg USWest, Ameritech, Bell South, etc.) are the best ones, and the little private/small company phones almost never work. On the interstates you'll find a lot of "$1 for three minutes to anywhere in the US" phones, and they usually won't work. You'll find that any given region usually has a couple of different payphone brands around, one of which will work.  My strategy is just to drive around trying all the different brands.  Sometimes, as happened to me in Indiana, I'll just be shit out of luck and not be able to find any workable phone.

Two things that will make your life easier when doing all this is turning the modem speaker volume up (so you can hear what's happening while you're connecting) and turning the "dialtone detection" off (so you can dial manually if the phone won't accept autodialing).  Click here for help with these configurations. 

If a payphone is "coupleable", you will usually be able to dial your ISP using your modem (autodialing), as opposed to manually punching in the number on the payphone. Some payphones that don't accept autodialing are still coupleable though, and by the time you've found out that it won't accept autodialing you've already got everything connected anyway, so it's worth a shot.  Get out of your car, dial the number manually, then start the connection process on your computer.  I wrote my dialup number on my coupler so I always have it handy when I'm dialing. 

One thing that can get really confusing is what happens when a payphone won't work:   you'll get error messages like "you're not using the proper configuration; change settings in control panel" or "the computer you dialed into got disconnected" or other things which would seem to have nothing to do with the coupler.  But don't worry, it's just that phone.  Go to another phone and it will work.

By far the most common indication that a phone isn't working with the coupler is that absolutely nothing happens.

Some tips:

Be prepared for a variety of reactions from people seeing this weird beast strapped to a payphone.  Some will think you're repairing the phone, some will think you're vandalizing the phone, and some will simply have no clue and stare at you.  Some who have "read something about this" in Newsweek or wherever will think you're a "hacker". It has been my experience that anyone who is internet savvy will be thrilled with what you're doing.

The ideal payphone has another one right next to it so people don't get pushy about you tying up the only phone.

There seems to be a trend in Interstate truckstops to provide wall phone outlets for the truckers to connect to the net.  I hope that catches on.   I know "TA" (Travelers America?) advertises this service.  If you find anything about this, let me know.

Get familiar with what happens when you click on the network icon at the lower right in Windows 95 (the small icon on your taskbar with the two computers).   It will display your connection rate, and will show when information is sent and received.  This can be handy when you're wondering if your connection has either frozen or you've been disconnected, as happens too often.  A really handy device would be a monitoring handset which you could connect to the line without affecting your connection.  It should be simple to make; if you make one, let me know how you did it.

I'd recommend either printing or saving this page so you have it with you while you're trying to uplink. If you're using Netscape, click file/save as. If you're using Microsoft Explorer, shame on you.


Definitely test your coupler on a house phone before venturing into the uncertain world of payphones.  Get comfortable with how it works, etc., so you'll be better able to isolate any problems.

Some payphones will work one day and not another.  I have no explanation for this.  I have found it useful when this happens to reboot.  It might always be useful to reboot before coupling.

Another problem I had was that my TDK pcmcia 56k modem was buzzing when I powered my laptop off a DC-AC inverter.  The buzz was audible through the phone line, so I could hear it over the speaker when I had the modem volume turned up.  The only solution I found was a) use the battery when dialing up or b) use the modem that came with my computer, which is slower but it gets the job done without buzzing.  I have no idea why there's a difference.

As I said, my ISP (Earthlink) has two 800 dialup numbers.  They are not created equal.  I usually get much better results from 800-853-7921, but it has a downside, which is that about 1/4 of the time I get a busy signal, which is a major pain in the rump when I have to walk back and forth between my van and the phone every time I'm going to redial.  The other dialup number, 800-350-6885, doesn't work as often but, interestingly, it's the only one of the two that I can get working in the San Francisco Bay area on the locally ubiquitous Pacific Bell brand payphones.

To make life a little more confusing, on the Konexx coupler there's a little unlabelled switch inside the battery compartment.  The manual describes the switch as toggling between "hi and low voltage modes".  My modem only works on the high voltage mode.  If you're having no luck, try switching this switch.

Nothing is more frustrating than getting disconnected from your ISP and having to go through the dialup process again.  My ISP recommended a few things to prevent being cutoff, and it seems to have helped.   Click here to see those recommendations.

Loud noises, like a truck passing or someone honking or yelling, will cut you off.  I've found a good way to minimize this is to wrap a towel around the coupler and phone.

If you're still having trouble, email me.

(I put these as appendixes instead of as linked pages so you'd be able to print the page and have everything together when you're sitting in your car futzing)

Turning your modem's speaker volume up:
1) go to control panel
2) click "modem"
3) click "configure"
4) turn the volume slider away from "off"

Getting rid of dialtone detection:
1) click "my computer"
2) click "dialup networking"
3) right click the connection you're tweaking (the one you'll use for coupling... if you have only one connection, fine, right click it)
4) click "properties"
5) click "configure"
6) click "connection"
7) make sure the "wait for dialtone" box is unchecked.

Getting rid of error correction: (I'm not sure what this is, but my ISP recommend I do it to make my connection more stable)
1. Double click on My Computer
2. Double click on Dial Up Networking
3. Highlight your connection icon by clicking on it once
4. Click on File
5. Select Properties
6. Click on Configure
7. Click on the Connection tab
8. Click on the Advanced button
9. Remove the check mark from the box labeled, "Use Error Control"
10. Click OK

Setting your FIFO Buffer: (whatever that is, but my ISP recommended I do this)
11. Click on Port Settings
12. Make sure that "Use FIFO Buffers" is checked
13. Slide both of the FIFO buffer settings all the way to the left
14. Click OK on each window until you have exited Dial Up Networking

Your ISP should give you tech support on how to do this stuff if you can't get it from my instructions.

-Hugh Mann
June 1998