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Build Your Own Chat-Cord

CmdrTaco posted about 9 years ago | from the because-you-can dept.

Hardware Hacking 164

Mr. Blond writes "Here is a description of how to build your own chat-cord for only 7 euro. This is a solder free version of the hack shown in this earlier Slashdot article. Now you can use any plain old phone to make calls over the internet, using Skype MSN-audio or any other VoIP software. Even the software from chatcord works fine with it, to make and accept calls using the buttons of your phone."

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jew the cord (-1, Troll)

programgeek (726420) | about 9 years ago | (#12984506)

jew the cord, LOLROFFLE

Re:jew the cord (0, Offtopic)

fr0dicus (641320) | about 9 years ago | (#12984821)

ich yog zich nit!

Re:jew the cord (0)

Anonymous Coward | about 9 years ago | (#12985935)

Jews did wtc

aarrgghghg (-1, Offtopic)

Anonymous Coward | about 9 years ago | (#12984508)

I'm a solder salesman you insensitive clod!

/.'ed? (1, Redundant)

bezgin (785861) | about 9 years ago | (#12984514)

Slashdotted so quickly? :(

Re:/.'ed? (0)

blastbeat (837011) | about 9 years ago | (#12984523)

Yup, it's down. Someone needs more bandwidth...

Re:/.'ed? (1, Funny)

Anonymous Coward | about 9 years ago | (#12984731)

It's not down, it's just that he's on the phone right now.

Re:/.'ed? (1)

tomhudson (43916) | about 9 years ago | (#12985007)

I got the Service Unavailable ... hed to check the URL to make sure I wasn't back on slashdot!

ok (-1, Offtopic)

Rackemup (160230) | about 9 years ago | (#12984522)

2 troll replies and the article is dotted already? Doesnt anyone use robust web servers anymore?

Re:ok (1)

dawnread (851254) | about 9 years ago | (#12984551)

I think everyone has gone straight to the article before they post - yeah right ;).

Or maybe the site is hosted via a line using this phonce cord?

Re:ok (1)

MyLongNickName (822545) | about 9 years ago | (#12984570)

Works fine for me.

(Whoa cowboy! You must have more than two fingers. Please chop the extra ones off, and repost)

Re:ok (0) (788350) | about 9 years ago | (#12984571)

We do, and we're holding steady just fine thanks.

Re:ok (0)

Anonymous Coward | about 9 years ago | (#12984907)

Maybe for the first couple minutes, but you're certainly not holding steady anymore.

Google Cache (5, Informative)

icemanuea (827734) | about 9 years ago | (#12984527)

Google Cache []

article text for those who are /.ed (4, Informative)

0110011001110101 (881374) | about 9 years ago | (#12984536)

Voice over IP is taking over the world and I also like the idea of calling for free... The problem I've experienced so far is the fact that you always have to use those cumbersome headsets. When it would be possible to use your standard phone for this application, the experience of VoIP would be much more like the real POTS (plain old telephone system). Especially a cordless phone with the base station near the pc would be nice. Furthermore it would be desirable to be able to use your normal phone keys to control Skype (or any other VoIP program). Christoffer Järnåker actually did a nice job eliminating this shortcoming with his Siemens Skype phone, . The disadvantage of this technique is that you kind of ruin your phone and that the procedure to create this kind of phone is different for every single type of phone.

Not too long ago I ran across a device called Chat-Cord ( This device does actually the same thing but it is placed between you phone and pc, not modifying your phone. But... This device is pretty expensive and I couldn't get it here in the Netherlands. Furthermore it seemed to me that this device actually isn't very complicated. So, after some internet research I somewhat found out how it worked and identified two difficulties to be solved.

In this article a description is given how to make your own chat-cord. It costs only like 7 euros. You have to solder some parts but it is very basic and simple.

To be able to use a normal phone to connect to the pc we have to make it look like for the phone as if it were connected to a normal telephone line and this telephone line has to look like it is making a call.

First of all the normal telephone line has a certain voltage, depending on the state of the line. On hook (waiting for incoming calls) is like 60V DC, ringing is 100V AC (roughly 100Hz) and off hook (an active call is going on) around 9V DC. So to be able to use a normal phone to make it think a call is going on, the phone has to see a 9V DC voltage at its input. This can simply be achieved with a 9V battery.

An alternative to this is to power the device from your USB port. It will only provide you with 5v instead of 9v, but this works fine in most cases. You have 300mA to your disposal there and that is more then enough. Just make sure you connect the right wires

The second part is the tricky part. A normal telephone system uses only two wires to send both the microphone and the speaker signal. From basic electronics you might know that you need 2 wires to send a signal, and at least 3 to send 2 signals, because one of the wires is acting as a reference (usually called ground). In a telephone system both the mic and the speaker signal are multiplexed into one signal. To be able to connect your phone to you mic-in and line-out of your pc you have to de-multiplex these signals.

The solution of Chris was to extract the mic an speaker signal before it is multiplexed inside the phone.

But this can also be done by a transformer (which is also used to prevent the 9V DC from going into you soundcard). The kind of transformer used for this application is a so called secondary centre tapped transformer. Meaning that it has 2 connections at its primary side (where the telephone will be connected) and 3 connections at its secondary side. The middle connection is physically connected to the middle of the secondary coil of the transformer. This middle connector is used as a shared ground for both the mic and the line-out.

Another issue is the input impedance of a phone line. When a phone line doesn't see the right input impedance reflections will occur, resulting in echoes or even in disabling the line. A telephone line has a input impedance of 600 Ohms, so the transformer has to be a 600 Ohm transformer. At the secondary side of the transformer a 150 Ohm resistor has to be placed at the middle connection to make the secondary input impedance 600 Ohm as well, resulting in a balanced transformer.

This all might seem complicated but as can be seen from this figure, the circuit is pretty simple and small.

For the connection to the pc jack-plugs have to be used, usually these are stereo. For the microphone connector the left and right signal can be simply connected to each other at the circuit connection, so actually you make it a mono signal. For the speaker connection one of the left or the right signal should not be connected because your soundcard stereo output would be shortcut otherwise. (In most scenarios this won't matter though as the sound from both channels are the same.) One funny thing is that it doesn't matter which connector you plug into mic or headphones. The result will be the same as we have the transformer in-between the two cables. For the telephone connector a RJ11 female connector should be used, so you can attach any phone to your device. Everything can then later be put into a nice little box, and -hey!- let's use a ADSL splitter. It will provide us not only with the RJ11 that we need but also a neat little box.

The software from Chat-Cord to be able to control Skype with your normal telephone keys ( ) works perfect with the circuitry, meaning that you can make and accept calls with your normal phone (not necessary to be at the pc when you make or accept a call). The only thing you need to do is to assign shortcut keys in Skype to your different contact persons, so you can call them with that number. Actually all this software does is to convert the DTMF signals from you phone (the different bleeps) to numbers , # and *.

I've tried the circuit with four different phones normal wireless, DECT, and wired and it all works perfect. You have a little bit of crosstalk between speaker and microphone (you hear yourself talking) but this is normal in telephony and it can be decreased with the volume control setting of your microphone (make sure you turn off the mic. boost).

So, let go through the steps in building one of these. I'm going to use a 9v battery as this is more 'fool proof', but if you're confident that you know what you're doing then go ahead an use power from the USB port.

This can either be build on a circuit board (like on the pictures) or like a bird nest. A bird nest means that you solder the wires directly on to each other and it doesn't look as good, but for a small project like this it should do fine.

First cut your pc plug (3.5mm stereo jack cable) cable in half, and strip of the wires. One is going to be used for the mic and the other for the speaker. You can have two versions inside this cable, either (a) with a shield (many small metal threads surrounding the other two cables) and two signal wires, or (2) three signal wires. If you have three wires you will have to figure out which one is ground, but it's usually black or yellow. If you have a shielded cable then the shield is the ground. We'll now have cable (A) and cable (B) looking the same. Take your transformer and connect pin 1 on the resistor to pin 2 of the transformer. Then on pin 2 on the resistor you attach both ground cables from the pc plug cable A and B. Connect one of the signal wires from cable A to pin 1 of the transformer. Connect one of the signal wires from cable B to pin 3 of the transformer. Connect pin 4 of the transformer to pin 2 of the RJ11 plug. Connect the + from your battery (or USB cable) to pin 6 of the transformer. Connect the - from the battery to pin 3 of the RJ11 plug. If you want to use an USB cable as power source then cut it off and strip down the wires. You will have red, back, white, green and a shield. Cut of white and green as we won't be using them. Red is +5v and black is ground. The shield can also be cut off, or if the transformer has a metal casing then you can connect it there. This would provide some extra shielding.

The following parts are needed for the circuit and the amounts I paid for it are as follows

9V battery 1.50 600 Ohm - 600 Ohm 1:1 transformer secondary centre tapped 2.50 150 Ohm resistor 0.10 Stereo jack cable (cut it in half to be used as mic and speaker plug) 2.00 Print board 5×5cm 0.50 6.60

If you can't find a transformer that is centre tapped only at the secondary side you can also use a transformer centre tapped at both sides and just not use the middle connector at the primary side (I also did this because I couldn't find a transformer centre tapped only at the secondary side). Just make sure it is a 600-600 Ohm 1:1 transformer. If you choose to use a battery in the circuit, it will last for a long time because no power is extracted from it during a call (otherwise we would be able to extract all our power from the telephone company ).

Theoretically you need at least 6v to the telephone but USB delivers 5v so what could be done then is to insert an IC that transforms 5v DC to 9v DC (a so called step up converter or DC-DC converter). In most cases the provided 5v will be sufficient, and if not - just hook up a 9v battery To make it the ultimate calling experience you would also want to make the telephone ring at an incoming call. As mentioned before 100V AC is needed for this. This can be created using a LM555 and a transformer and maybe one transistor. The difficulty is to detect when Skype is ringing... I haven't got a clue how to do this in hardware...

Good luck!! And have fun Skyping all around the house...

For questions you can reach me at:

Re:article text for those who are /.ed (4, Interesting)

Technician (215283) | about 9 years ago | (#12984770)

Thanks for the text.

You have a little bit of crosstalk between speaker and microphone (you hear yourself talking) but this is normal in telephony and it can be decreased with the volume control setting of your microphone (make sure you turn off the mic. boost).

For those who know about impedance, and how a sidetone coil works, it would be easy to finish the project and cure hearing yourself loudly. It is possible to match a phone with a proper hybrid and have very little crossover of the mike and earphone on a single pair of wires.

There are plans on the internet for op-amp as well as transformer telephone hybrids that do an excelent job of seperation. Properly adding series resistance from the sound card to provide proper source impedance helps a lot. A telephone hybrid works good if the sound source is near 200 ohms, not the less than 20 ohms of a sound card output.

Re:article text for those who are /.ed (1)

tmasssey (546878) | about 9 years ago | (#12984942)

Echo due to hybrid circuits is a *major* problem with analog to VoIP hardware: particularly these [] analog boards. Part of the TDM boards' sensitivity to speicific lines is believed to be poor impedance matching. I've looked for hardware techniques for flexible impedance matching circuits I could experiment with. Unfortunately, I've found *very* little outside of "throw this cap and potentiometer on the line and see what happens...".

Would you have some links that illustrate what you're talking about? As soon as I finish posting this, I'm going to be googling "sidetone coil"! But if you or anyone else have any other thoughts...

Unless you're purely talking about enhanced hybrid to separate conversion circuits. *Those* I've seen, but that's not what we need. That's internal to the board, and we don't get to play with that! :) However, anything that allows us to improve the connection between the board and the POTS line, particularly in the area of impedance matching, wouldbe *much* appreciated.

MirrorDot (2, Informative)

cd_serek (681446) | about 9 years ago | (#12984542)

MirrorDot [] .

This Sounds Like A Good Cottage Industry (3, Interesting)

DanielMarkham (765899) | about 9 years ago | (#12984546)

If I were this guy, instead of posting the directions on the blog, I'd be making little kits to sell on E-bay or something. This could be a useful little widget for all those new millions of Skype customers out there.
I'm not sure about product liability though -- I wonder if it's possible to completely disclaim any possible harm that could be caused to your phone or computer. Maybe a big red sticker that says, "You're an idiot if you plug this up! Warning!"

NASA blows up comet, gets sued for $300 million []

Re:This Sounds Like A Good Cottage Industry (0)

Cthefuture (665326) | about 9 years ago | (#12984815)

In most countries there are regulations and certifications needed for phone equipment.

This thing doesn't let you control Skype with the phone though... meh...

A better system would be to use all USB. It could be used as a USB audio device (mic and speaker), could control the software, and only require a USB cable to hookup. This would obviously be more complex than this project but would be a lot more practical.

Re:This Sounds Like A Good Cottage Industry (1)

Mister Blond (897449) | about 9 years ago | (#12984950)

Actually this thing does let you control Skype with your phone. Just use chat-cord's software: [] and you can use your telephone's keys to accept and make calls in Skype (you just have to assign each contact to a speeddial number)

Re:This Sounds Like A Good Cottage Industry (0)

Anonymous Coward | about 9 years ago | (#12985046)

Most countries has regulations for connecting things to the telephone lines, this only connects the phone to your computer. In other words, no regulations!

Re:This Sounds Like A Good Cottage Industry (1)

RGRistroph (86936) | about 9 years ago | (#12985498)

If you use the serial port instead of USB, and a PIC chip and a MAX232, you could do it fairly cheaply.

Re:This Sounds Like A Good Cottage Industry (2, Interesting)

sunwolf (853208) | about 9 years ago | (#12985383)

If I were this guy, instead of posting the directions on the blog, I'd be making little kits to sell on E-bay or something.
you weren't one of the guys moaning about how Roland Piquaville makes money out of slashdot, were you?

Re:This Sounds Like A Good Cottage Industry (1)

skids (119237) | about 9 years ago | (#12986072)

Well, that sounds like a chore. First you have to do the same damn thing over and over again, and determine how much to charge based on how much time and materials it takes. Then you have to advertise, and then deal with the sales mechanism and all the irregularities in orders that inevitably pop up. Then some several months down the road, if you have any success at it at all, some Chinese company will catch on and start underselling you.

Such things are better left for fun and amusement [] .

Erm (5, Informative)

tunnie (730907) | about 9 years ago | (#12984567)

This is a solder free version [...]
You have to solder some parts [...]

Re:Erm (1)

vidarlo (134906) | about 9 years ago | (#12984675)

I built it without [] soldering...

Re:Erm (2, Informative)

Mister Blond (897449) | about 9 years ago | (#12984781)

What is ment is that you don't have to solder inside your phone to make it work. An earlier version required soldering inside your phone possibly damaging your phone...

Tis great, but... (1)

Ranma-sensei (800217) | about 9 years ago | (#12984572)

personally, I don't really need it. I like to have my hands free when talking, so I'll stick to my good ol' headset. ;)

Depends on the call (2, Funny)

handy_vandal (606174) | about 9 years ago | (#12984600)

personally, I don't really need it. I like to have my hands free when talking, so I'll stick to my good ol' headset. ;)

Depends on the nature of the call -- in some cases, I only need one free hand ....


WHY???? (0, Offtopic)

chrisnewbie (708349) | about 9 years ago | (#12984578)

Why pay 7 euro to use a phone VOIP + your regular phone line....that is totaly crazy.

Just switch to VOIP entirely and you actually pay less, unless you dont have access to it.

But again, most phone companies give you rebates in the week after 18h00 for long distance calls , so you really need to to do your math before paying extra to get VOIP while still holding on your regular service.

i get VOIP for 24.99 (cdn)a month with unlimited long distance calls in canada + voicemail.

Re:WHY???? (1)

SubTexel (715118) | about 9 years ago | (#12984688)

Because that 7 euro is a one time deal, not like your monthly charge of 24.99...

Re:WHY???? (1)

chrisnewbie (708349) | about 9 years ago | (#12984849)

ha o.k! Then it's moslty good for people who do long distance calls on a regular basis.

Re:WHY???? (1)

autocracy (192714) | about 9 years ago | (#12984762)

You missed the point. It allows you to switch to VOIP entirely, but still use the same LINE EQUIPMENT. Basically, I could make VOIP calls while using my phone I already have. Nice if you have a good cordless phone, eh?

Re:WHY???? (1)

chrisnewbie (708349) | about 9 years ago | (#12984868)

You still need to pay for your phone service unless you have cable for internet, but again will you not need a phone number so people can call you? if i'm not mistaking you still need to pay for that unless the companies who offer this services also provides you with a number so you can receive incoming calls.

Re:WHY???? (1)

bhima (46039) | about 9 years ago | (#12985381)

I suggest you go to Skype's home page a read up on what skype does, then you will not be so confused. It's great, It works, and It's worth the 7 Euro.

Re:WHY???? (1)

morgan_greywolf (835522) | about 9 years ago | (#12984910)

I use Vonage. I have switched to VOIP entirely. I pay $24.99 (U.S., per month) and I have a regular cordless phone. I have a phone number, voicemail, caller ID, call waiting, three-way calling, all that. Tell me what this piece of equipment offers me.

Re:WHY???? (1)

ShortBeard (740119) | about 9 years ago | (#12984992)

I agree. It looks real neat. I could use it with my friend in Mexico. We use voip sw and email each other to schedule.
But no phone number is a stumbling block.

Seeing how I'm going voip with a comapny that will provide a phone number and such I don't see building this device or buying the chatcord ($50).

Re:WHY???? (1)

harrkev (623093) | about 9 years ago | (#12985386)

And then when the power goes out, so does your phone. A UPS might buy you a few hours or so, though. But if your power is off all day, there goes your phone.

Also, during a disaster, internet and cable service does not get the same level of attention that power and phone does, so you could be withoug a phone long after your neighbors are chatting it up with their relatives.

But then again, I might be biased. I just had three hurricanes come near my home in the last year. I was out of power for a combined total of around two weeks.

I would not have a problem with VOIP as a 2nd phone line, but I still want to keep one POTS line around just in case.

Re:WHY???? (1)

SillyNickName4me (760022) | about 9 years ago | (#12985497)

I think you are right with regards to what gets priority. That said, I very clearly recall sept 11. and talking to people pretty close to the World Trade center using the Internet, but not being able to reach them by phone.

Somehow the IP network seems to be more resistent to partial failure then the phone network.

Re:WHY???? (1)

mikewas (119762) | about 9 years ago | (#12986192)

The phone network didn't fail ... it was overwhelmed!

The phone network guarentees a quality of service, so there's a sharp cutoff to how many simultaneous users there are. If a trunk group is designed for n users then user 1 through user n will each get an 8kbps pipe but users >n get a fast busy. Conversely, if there are less than n users those users don't get better service.

The internet has no such guarentee, so as traffic increases it degrades. So if the path is designed for decent response for n users, the n+1 user still gets on but all users from 1 through n+1 get slightly degraded service. If there are less than n users then service is generally better than the standard.

Why not just use a modem? (1)

kaos.geo (587126) | about 9 years ago | (#12984593)

After reading TFA y think it would be possible to use a modem as input for the telephone. Is this possible, difficult? I am just pitching the idea. Anyway this chatcord is a nice project for this weekend!! heee! :P

Re:Why not just use a modem? (2, Insightful)

tmasssey (546878) | about 9 years ago | (#12984970)

A modem is not designed to interface with the phone side of the connection. It only interfaces with the line side. This hack basically allows you to use the handset of your phone as a mic input and speaker output. A modem isn't going to help you here.

Now, if you have a very fancy modem that does full-duplex voice (most only do half-duplex voice), you could use the modem instead of the sound card. But that doesn't save us very much: most people already have a sound card...

Re:Why not just use a modem? (1)

kaos.geo (587126) | about 9 years ago | (#12985671)

Thx for the clarification....- Now I have a qualified opinion, therefore an excuse to spend most of my saturday soldering away!! ;)

VOIP is great! (1, Interesting)

Cmdr Whackjob (883018) | about 9 years ago | (#12984622)

I use Lingo [] as my exclusive phone service - I cancelled my POTS line after two days - SBC was very difficult to cancel when I told them I was going to VOIP

I have had absolutely no problems for the last two months. I get an amazing price - $19.99 for unlimited US, Western Europe & Canada, and the first three months absolutely free.

I can't imagine not having the convenience of VOIP. The online bonuses - email voicemail, detailed billing, etc are good too.

The rates to the rest of the world are good too

Re:VOIP is great! (-1)

Anonymous Coward | about 9 years ago | (#12984653)

How is the quality on Lingo? I've considered them in the past.

Re:VOIP is great! (2, Informative)

2$ Crack Whore (813937) | about 9 years ago | (#12984680)

Surprisingly there are a bunch of low cost carriers who route their calls over VoIP when going overseas so they can fit more calls into the same pipe. A lot of said countries are in the third world. Of course, whether you can get decent IP service when you don't have leased T1s is a different story :-)

Anyway, you can test your VoIP quality from anywhere with IP and a Java-enabled browser at [] if you are concerned about your IP quality not being up to snuff, or if you want to see how it is and you are in the wilds of Africa... but have IP connectivity.

Re:VOIP is great! (0)

Anonymous Coward | about 9 years ago | (#12985563)

Almost all calls are routed over undersea ATM, and are functionally identical to VoIP, except they have dedicated fiber, and calls aren't routed over the internet at large, and aren't routed over IP for that matter.. Not that it's that big of a difference.

Neat tester though, thanks for the link.

Re:VOIP is great! (0)

Anonymous Coward | about 9 years ago | (#12985032)

So everything's rosey until your internet connection goes down and you need to call your ISP to fix it... ;)

Re:VOIP is great! (1)

Lumpy (12016) | about 9 years ago | (#12985869)

I also think it's great, but you are WAYYY too optimistic.

I can't imagine not having the convenience of VOIP.

I can, when the cablemodem goes out. Having to use up 30-60 minutes of my cellphone time to call the cable company to report the outage and sit on the phone with a numbnut that asks, "is the cablemodem on? do you have it plugged in? do you really have a cablemodem? try, this,this,this... just a minute.... we are having trouble in your area, call us back in 4-6 hours bye... click..."

Oh that is enjoyable when you are not sure if you are near the limit of your minutes that month.

Simpler (almost cheaper) better looking hack (1)

Arthur B. (806360) | about 9 years ago | (#12984626)

Why not plug the phone directly into a RJ11 slot ? (a 56ko card actually is ~10euro + you don't trash your existing phone). I guess once this is done everything else is just software...

Re:Simpler (almost cheaper) better looking hack (0)

Anonymous Coward | about 9 years ago | (#12984707)

Well, other than "because it won't work," there's no reason not to do this.

Notice that a modem plugs into a jack that connects to your telephone company as well - this circuit attempts to emulate the *phone company* side of the connection, not the phone side. Modems do not provide the constant voltage source required to act as the phone company side of the connection, nor do they provide ring or on-hook signalling (although the circuit in the article does not either).

Re:Simpler (almost cheaper) better looking hack (2, Informative)

NoMoreNicksLeft (516230) | about 9 years ago | (#12984739)

Yeh, if you have one of the asterisk digium cards (or any other FXO card for that matter). If you just have a crappy internal modem, it *might* be possible, supposing whether or not it has an answering machine feature, or is a winmodem whose chipset you can reverse closely enough. If it's a plain modem, you'll never force voice quality sound through it in either direction.

Re:Simpler (almost cheaper) better looking hack (1)

RGRistroph (86936) | about 9 years ago | (#12985467)

To use a normal telephone with asterisk you need an FXS card, not an FXO. FXS cards are significantly more expensive than FXO. You can get a PCI card that has slots to stick in little mini-cards and get 4 FXO lines for about $500. Comparitively, an FXO card is $7 on ebay.

Another way to use a normal telephone is to get a Digium "IAXy" device or Cisco ATA 186. These are small boxes that have an ethernet on one side and a RJ11 on the other. This still ends up around $100 per real telephone.

That's why there is so much interest in a much cheaper way to use a real telephone or at least a normal handset of some time with a computer softphone.

This device requires that your software be smart enough to use the DTMF tones. If you are willing to give up being able to dial from the handset, there is a simple handset that is a "Y" connector that connects both to your speakers and to the soundcard; picking up the handset automatically mutes the speakers. I can't find the link to it right now. (It's not cordless, which seems to be the main goal of many of these hacks.)

Re:Simpler (almost cheaper) better looking hack (1)

ShortBeard (740119) | about 9 years ago | (#12985693)

A quick Google and here [] you go.

Looks real economical.

Re:Simpler (almost cheaper) better looking hack (1)

tmasssey (546878) | about 9 years ago | (#12985060)

I've posted about this in another post, but I'll re-write here...

A modem is designed to interface with the phone line, not the phone handset, so a normal modem won't help you talk to a handset at *all*. This hack is designed to use the speaker and mic of a phone as the input and output of a sound card. Nothing more. Most voice modems are only half-duplex, so they won't help you, either. If you had a fancy full-duplex voice modem, it would allow you to replace the entire sound card, but then you'd have to make Skype work with that instead.

Basically, what you're asking for is what is called an FXS interface (not an FXO, as others have mentioned in this thread). They do exist: they [] make one, for example. However, they're not inexpensive. This cable costs less than $7: that's hard to beat.

A note about the software (1)

SuperDuh (13356) | about 9 years ago | (#12984633)

From TFA:

This software is still in testing phase and is available from our Download Section free of charge and "as-is". Expiration date November 1st, 2005.

Any idea how easy it'd be to do an OSS version of this?

Re:A note about the software (3, Informative)

NoMoreNicksLeft (516230) | about 9 years ago | (#12984710)

Would need to monitor the mic in channel on the soundcard, listening for DTMF tones. The tones themselves are pretty unmistakable if I remember, almost impossible for random noise to approximate them.

how is this solder free? (0)

nealrs (75987) | about 9 years ago | (#12984640)

seriously. how?

Warning - USA/Canada is Different (5, Informative)

SirCyn (694031) | about 9 years ago | (#12984643)

I just want to warn everyone that he is in the Netherlands. I know it's not exactly revelant to this project, but telephone standards are fairly different in the USA and Canada.

We use 48v @ 20Hz to ring.
On Hook is 52v at 300 to 1800 ohms.
Off hook is 12v at 680 ohms (ideal).

Re:Warning - USA/Canada is Different (2, Informative)

pe1rxq (141710) | about 9 years ago | (#12984773)

Which isn't that different from what we have here in the Netherlands...
This thing isn't anything like a real telephone line but approximates it enough to get audio in and out off the telephone and supply the telephones logic.


Re:Warning - USA/Canada is Different (1)

SirCyn (694031) | about 9 years ago | (#12984887)

Very true, I'm just worried about people trying to build more complicated projects, based on this one.

I don't want people assuming that phones are the same all over the world, most people wouldn't think twice that a North American phone wouldn't work in Europe, and vice-versa.

Re:Warning - USA/Canada is Different (1)

SillyNickName4me (760022) | about 9 years ago | (#12985351)

Hmm.. the AT&T 5400 cordless I bought in the USA in the early 90s worked quite fine on a telephone line in the Netherlands..

Most analog modems around are the same regardless of buying them in the USA or Europe for example (I used to own a whole lot of US Robotics modems imported from the USA when I was still running a BBS, and again they worked fine on a Dutch telephone line, and the official Dutch importer for US Robotics confirmed that they are in fact identical when I was at one of their technical sessions)

I know the systems are different, but they are similar enough for things to usually work.

Re:Warning - USA/Canada is Different (1)

afidel (530433) | about 9 years ago | (#12984867)

48v is the standard, real life shows anywhere from 40v to 150v. The minimum is 40Vrms (delivered into a 5 REN load). Not sure where you would ever see anything over 100v, but aparantly it does happen.

Re:Warning - USA/Canada is Different (1)

tmasssey (546878) | about 9 years ago | (#12985087)

Ring voltage can be well over 100V...

Re:Warning - USA/Canada is Different (1)

Frank T. Lofaro Jr. (142215) | about 9 years ago | (#12985581)

I am in the USA, and we sure do have a strong ring voltage.

I know, I felt it (back in NYC), and it wasn't pleasant (admittedly it wasn't extremely painful, but it had a bite).

Battery or USB power not necissary (1)

moroderzone (585335) | about 9 years ago | (#12984648)

There was a comment that said on self powered phones, like cordless phones, you could skip the Battery or USB power source.

A common phone recorder will work? (1)

soulhuntre (52742) | about 9 years ago | (#12984659)

From a related page [] we see this comment...

"It's just the classic phreak box "The Rock Box" or a Rat Shack phone recorder, but it's the idea that counts. Great idea!"

Assuming they mean this Radio Shack Recorder Control [] then I already have what I need... the question is am I understanding it right? Will it work?

Re:A common phone recorder will work? (1, Interesting)

Anonymous Coward | about 9 years ago | (#12984745)

Should work... all his device does is split the phone line audio to separate input and output signals for your sound card. Your phone line recorder does the exact same thing. The real workhorse in this setup is the software that you need to download which does the DTMF decoding and integration with Skype.

Re:A common phone recorder will work? (2, Informative)

enosys (705759) | about 9 years ago | (#12985072)

A friend got something like that from Radio Shack and it fried his sound card. He opened it up and found that it was just a direct wire connection, with nothing to protect the sound card from the high ringing and on-hook voltages found on phone lines.

I don't know if that's the same thing he got, and in any case hooking it up to a phone (not the phone line) should be safe.

Grammar Nazi (1, Interesting)

Anonymous Coward | about 9 years ago | (#12984711)

Let it be noted that the plural of euro is euros.

Re:Grammar Nazi (-1)

Anonymous Coward | about 9 years ago | (#12984722)

Let it be noted that you are not going to get laid anytime soon.

Re:Grammar Nazi (4, Informative)

nepheles (642829) | about 9 years ago | (#12985291)

Let it be noted that the plural of euro is euros.

Let it also be noted that you are wrong. The plural is euro. It was decided that having different plurals for the different European languages would lead to too much confusion.

This Euro FAQ [] published by the EU clarifies things.

Re:Grammar Nazi (1)

ebvwfbw (864834) | about 9 years ago | (#12985596)

Let it also be noted that you are wrong. The plural is euro.

You did read the FAQ you pointed to, didn't you? The spelling seems to depend on where you are. For France, it is Euros (100 Euros it says, Les Euros). Since French is the Universal language of Diplomats, it would seem that you are the one that is wrong. At the very least, I wouldn't say he is wrong because it depends. Of course this may all be academic soon if they dump the Euro as many countries seem to want to do.

Re:Grammar Nazi (1)

blonde rser (253047) | about 9 years ago | (#12985846)

Since French is the [u]niversal language of [d]iplomats[...]

Wow. This has to be one of the finer examples of constructing a complicated argument just to prove someone wrong. The pdf says right at the top that it is referring to different languages not different places. Since this discussion is in English the proper spelling to use is the English spelling. I think this is the simplest argument. Is there really a reason to draw the diplomats into this?

Re:Grammar Nazi (1)

Roger W Moore (538166) | about 9 years ago | (#12986013)

Anyone noted the irony that we don't actually use the euro in England? My guess is that whe we do the plural we be "euros" and all the declarations to the opposite will be about as effective as king Canute.

Son of the Grammar Nazi (1)

bwcbwc (601780) | about 9 years ago | (#12986014)

Context also needs to be taken into account. For example, if you buy a 30 dollar sound card it costs 30 dollars. So be sure you're talking about a true plural and not an adjective phrase.

Make and accept calls using the buttons?!?!?!? (0)

Anonymous Coward | about 9 years ago | (#12984723)

I don't think people are yet ready for this. Way too futuristic. Once they are used to immortality and flying cars, maybe we can roll out the using of buttons to make and accept calls. Until then, it will be too much danger like the krell machine.

solder-free? I think not. (0, Redundant)

Ronnie Coote (251572) | about 9 years ago | (#12984733)

From TFA: "You have to solder some parts but it is very basic and simple."

Ummm (5, Insightful)

white1827 (848173) | about 9 years ago | (#12984760)

The real chat-cord [] only costs $24.95 USD. This solution would cost $8.33USD by using raw Euro to USD conversion. For this little savings, I would just buy the chat cord and get the included software that works for windows and mac.

mod parent up (1)

enosys (705759) | about 9 years ago | (#12985108)

That's nice to know. I'd rather build my own but I'm sure most people would rather buy that.

Chat cord software is free (1)

enosys (705759) | about 9 years ago | (#12985213)

The chat cord software is free. Here is a page with information and download links [] . First you need to login to [] . You can get logins through [] . Then follow the download link and you'll be able to get to the actual download page.

Alternatively, here are direct links to the files: DialerXT [] and DialerSK (for Skype) [] . I'm not sure if these would work for everyone. I'm including them because this way would be much simpler.

Solder (0)

Anonymous Coward | about 9 years ago | (#12984810)

What's wrong with solder anyway?

No external sound (2, Informative)

RikF (864471) | about 9 years ago | (#12984853)

The only problem I have with solutions like this (and the headsets) is that unless you have 2 sound cards you are limiting yourself to only being able to hear the PC sound if you pick the phone up! USB solutions which count as an additional sound card allow you to direct VOIP (say Skype) to the phone and all other sound to the sound card. Skype also allows you to have the ringer run on the speakers and the phone, incase the ringer on the USB phone isn't loud enough. I have one of those orange Skype phones and apart from the awful ringer it is superb - excellent sound quality


Dont need this (1)

ickleberry (864871) | about 9 years ago | (#12984945)

My nokia HDW-2 works fine with skype, on linux :)

7 Euro? (-1, Offtopic)

Anonymous Coward | about 9 years ago | (#12984978)

Chat-cord seven euro? Sucky sucky five dollar, me love you long time.

Busy Tone... (0)

Anonymous Coward | about 9 years ago | (#12985090)

Sorry, the user you are trying to reach has been slashdotted... Please try again later.

Patent Pending (1)

pointym5 (128908) | about 9 years ago | (#12985141)

According to the ChatCord website, they're patenting the idea. Once that happens, home-made ChatCords will be in violation of the company's intellectual property rights.

Re:Patent Pending (1)

ablcmx (105873) | about 9 years ago | (#12985256)

Silly - prior art would include telephone headset adapters and so many other things I don't even want to list them. But that, of course, never stopped a patent from being granted in the past.

FUD (1)

ImaLamer (260199) | about 9 years ago | (#12985371)

home-made ChatCords will be in violation of the company's intellectual property rights

That isn't true at all! The only thing in violation would be someone else making it for you (and giving or selling it to you).

It is totally legal to build one at home and use it personally - there isn't anything wrong with that. Patents keep others from launching a commercial venture with your idea.

coincidence!.. and also need help (0)

Qa32 (823982) | about 9 years ago | (#12985278)

well, while I was reading this article and coments here, /. was flashign Vonmage ads on top and it sure was kinda ironic, that this ad had to flash when the need was to eliminate service like theirs and build your own. also, all these 1-800 #s (cust support)most goto the Asia, and they are "Toll Free", (and most of the times the stupid call is for 30 mins, with 25 mins hold time) but wtf, when I need to call someone genuinely in Asia, even if its for 5 mins, I frickign have to shell out. Can there be something done about this and start getting VoIP calls to phone lines for cheap/free. Its sad that there has been done nothing so far. I would not even mind paying 20 bucks a month for unlimited calling there (Asia). Any answers...

Pah! (3, Funny)

Zwets (645911) | about 9 years ago | (#12985479)

I know a much cheaper way to make your own chatcord. It involves two cans and some string..

Re:Pah! (0)

Anonymous Coward | about 9 years ago | (#12985888)

Is that the real solder free version?

What's the Point? (1)

dbucowboy (891058) | about 9 years ago | (#12985521)

Doesn't every person in the world have a cell phone by now?

Re:What's the Point? (1)

Eric604 (798298) | about 9 years ago | (#12985812)


yofu Fail It (-1, Flamebait)

Anonymous Coward | about 9 years ago | (#12985834)

com8on knowledge to decline for

mod Down (-1, Offtopic)

Anonymous Coward | about 9 years ago | (#12985992)

world-spaaning become an unwanted CLEAR SHE COULDN'T

Why draw the line at half-assed? (1, Informative)

Anonymous Coward | about 9 years ago | (#12986167)

When you can get an Handytone [] or IAXy l&category=hardware&product=S101I/ [] type device anyway? I mean, really, get a job, these things only cost $100.... Oh, yea, and feel free to start the ususal rant about proprietary systems and how much they is skype right? Or is it only lame when proprietary isn't free?
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