Build Your Own Chat-Cord

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."

Comments

Re:/.'ed?

[blastbeat]

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

Google Cache

[icemanuea]

Google Cache

Woah, instant /. effect

[Anonymous Coward]

Google's cache: http://64.233.179.104/search?q=cache:_pO1ist8fxMJ: www.grynx.com/index.php/projects/build-your-own-ch at-cord/+&hl=en&client=firefox-a

article text for those who are /.ed

[0110011001110101]

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, www.grynx.com/index.php/projects/siemens-skype . 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 (www.chat-cord.com). 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 i

Re:article text for those who are /.ed

[Technician]

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

[tmasssey]

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.

Re:article text for those who are /.ed

[Anonymous Coward]

I design echo cancellers for telephone networks, so I know a little bit about this problem. My company can get a little paranoid about what people post on public sites, so I'm posting this as AC.

Anyway, impedance matching will help, but unless it's perfect, you won't totally get rid of the echo. Telephone networks install echo cancellers to get rid of the echo due to reflections in the hybrid. Products like this and this. can make echo virtually inaudible even when the echo return loss is only 6dB. Products like this represent the state of the art, but the echo cancellation algorithm doesn't need to be too complex to get very good echo cancellation. There are a lot of local carriers and long distance providers that are still using echo cancellers they bought in the 1980s. If you think about what kind of processing power was available for implementing DSP algorithms in the 1980s, you can see that a good echo canceller doesn't require a lot of resources.

A basic echo canceller would use a LMS adaptive FIR filter to model the echo path and then subtract off the echo. It should be easy for even a very basic algorithm to reduce echo by 20 or 30dB. If you started with very high echo, you might want to add in a center clipper as well to remove any residual echo that the FIR filter couldn't take care of. Any experienced DSP guy ought to be able to design a reasonably good echo cancellation algorithm in a matter of hours.

I think a software approach is the only way you're going to get anything that sounds as good as a POTS phone on a real telephone network. Adding a little DSP code to Skype for this task seems like the easiest and cheapest way, but you could also do it on an external DSP if you prefer to have the echo canceller built into the cable. I'd be willing to offer a little assistance with the DSP work if someone is seriously interested in taking on a task like this.

Re:article text for those who are /.ed

[Anonym1ty]

When figuring out what type of transformer you need to match, the turns ratio is the square root of the impedance ratio.

The problem comes in that a transformer will cause an equivalent voltage increase, much more than you want. a 1:1 ratio 600-ohm-to-600-ohm audio transformer is what you want.

So rather than an impedance matching coil, a 10K Ohm in series with a 500 Ohm potentiometer is what you want. -That's why everyone keeps telling you to try a Resistor and a Pot. You want to match the levels here and you don't want to send too much voltage into the wrong thing.

What will happen when you make the circuit this way is you will find you have more control of the audio when using the sliders in the mixer control panel. Without these, you will find the "sweet" spot will be an unattainable value... either too high or too low and impossible to find a value just right in between. With this circuit, you will find the "sweet" spot will have been spread out so you have a larger area of useful adjustment in the audio mixer control. ---And if you can adjust your mic/spkr levels finely enough you can eliminate those icky echoes.

Re:article text for those who are /.ed

[Anonymous Coward]

Interestingly enough, eliminating that crosstalk might not be desirable.

When I worked for a telecom company, we had to build a simple digital phone into one of our products, for voice comm between sites (techs use this fairly often). One of the complaints that kept coming back from technicians had to do with that inter-site phone: they couldn't hear themselves on it.

Turns out, a lot of folks take that feedback to the earpiece as an indication that the phone is actually working. It's a holdover from the old days when phones really had too much crosstalk between microphone and earpiece, and a lot of folks don't trust a phone that doesn't give them their own voice back.

I wound up writing some code that would take the microphone sample, scale it down a bit, and add it back to the audio out. After some experimenting with the levels, the complaints stopped.

Food for thought.

Re:article text for those who are /.ed

[Technician]

Turns out, a lot of folks take that feedback to the earpiece as an indication that the phone is actually working.

That is exactly why the local DJ at the radio station uses a commercial Hybrid with a deep null to prevent feedback and a telephone calls their hybrid a sidetone coil. It provides the audiable feedback users expect from a telephone so they know it's working.

MirrorDot

[cd_serek]

MirrorDot.

This Sounds Like A Good Cottage Industry

[DanielMarkham]

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

[Cthefuture]

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

[Mister Blond]

Actually this thing does let you control Skype with your phone. Just use chat-cord's software: http://www.chat-cord.com/iframe_dl.htm#dailer 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

[Anonymous Coward]

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

[sunwolf]

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

[RGRistroph]

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

[skids]

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.

Re:This Sounds Like A Good Cottage Industry

[fm6]

A pre-made chat cord costs $30. Hard to undercut that. Besides, Hackers love to share.

Every story in Hardware Hacking gets at least one post by somebody who doesn't grasp that HH is not an economically sustainable activity. Mass produced electronics is too cheap for hand-made gadgets to compete. Hackers know this: they do it mainly for fun, and for self-education. Some are also broke enough to need to save the few extra bucks the off-the-shelf item costs.

Re:ok

[dawnread]

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?

Erm

[tunnie]

This is a solder free version [...]

TFA:

You have to solder some parts [...]

:/

Re:Erm

[vidarlo]

I built it without soldering...

Re:Erm

[Mister Blond]

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...

Re:Erm

[Anonymous Coward]

That's "free" as in speech.

Re:ok

[MyLongNickName]

Works fine for me.

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

Re:ok

[Bit-tech.net]

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

Tis great, but...

[Ranma-sensei]

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. ;)

WHY????

[chrisnewbie]

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????

[SubTexel]

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

Re:WHY????

[autocracy]

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????

[chrisnewbie]

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

Re:WHY????

[chrisnewbie]

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????

[morgan_greywolf]

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????

[ShortBeard]

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????

[bhima]

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????

[harrkev]

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????

[SillyNickName4me]

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????

[mikewas]

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.

Re:WHY????

[SillyNickName4me]

I am aware of that, but the result is still that the internet allowed communications to go on while the phone network did not.

The phone network is also quite sensitive to an exchange failing in the path between 2 points while an IP network usually deals well with one of the routers failing.

Degraded service is often better then no service at all.

Re:WHY????

[morgan_greywolf]

The question wasn't what POTS offers me over VOIP (I already know that)...the question was what the 'chat cord' in the article offers me.

Re:WHY????

[jacksonj04]

The IP network is designed to deal with partial failure, that's the whole point :D

What happened with the phones (Note I'm assuming the US has the same response plans as the UK here) is that once an emergency was declared, anybody who didn't need the bandwidth was unplugged so that emergency service calls were guaranteed to get through. This is standard emergency procedure, and makes sure the exchanges aren't overwhelmed with people ringing to check other people are ok, and instead that 911 calls and calls between emergency personnel can get through.

This is also noticeable on cellphone networks, where signals will be dropped for everybody who doesn't need mobile access during an emergency.

Re:WHY????

[mikewas]

If there's a failure, then communication gets routed around it. Is service degrade? Possibly, since the path is usually much longer, but the degradation is held within limits.

There's a lot happening with packet based voice communications, and much of it is centerred around Quality of Service.

Re:WHY????

[autocracy]

Aaaargh.. you don't get it! :-P Your phone number would come across the VOIP service. What this device offers is to have a real telephone hooked to your computer instead of earphones and a microphone. Whoever provides the service will provide a number. This device is not a service... it's like a DB9 serial to USB adapter, only it's telephone handset or basestation to speaker and microphone jacks.

Re:WHY????

[autocracy]

This equipment offers you nothing that you don't already have. Whatever your cordless phone's base station plugs into is doing the job that this device otherwise would. This is a way to make your own if you didn't get something like that.

Re:WHY????

[SillyNickName4me]

No doubt they are catching up, matter of fact is that I experience COMPLETE failures in the phone network more oftenn then on IP networks. That things are improving is all cool and well, but does not change how things were and are, only how they are going to be (and that maybe)

Having worked at Phillips natlab in a combined IBM/Phillips/KPN ISDN and PSTN telephony project for the Dutch government for 5 years, being responsible for debugging all the failures in the ISDN setup, I do think I have a bit of a clue what I am talking about btw.. it is not like I do not know how those networks work.

My initial comment was to provoke some thought, not to seek answers as to why they are different.

Re:WHY????

[SillyNickName4me]

The IP network is designed to deal with partial failure, that's the whole point :D

Yes... I do believe that was the exact point I was trying to make.

(I have dealt with both very intensively as an engineer, my "question" was to provoke some thought, not to seek answers as to why this is as it is)

What happened with the phones (Note I'm assuming the US has the same response plans as the UK here) is that once an emergency was declared, anybody who didn't need the bandwidth was unplugged so that emergency service calls were guaranteed to get through.

And who is the government to decide who needs emergency services? (see below)

This is standard emergency procedure, and makes sure the exchanges aren't overwhelmed with people ringing to check other people are ok, and instead that 911 calls and calls between emergency personnel can get through.

1. 10000+ people calling 911 about the same emergency is not going to help anyone and is still going to cause overload.
2. Emergency services that depend on the phone network for their internal communications are not going to be very reliable. Any emergency service here (the Netherlands) has its own wireless communications system that is completely independent of the phone network. I would be rather surprised to find that that is different in the USA or the UK.

This is also noticeable on cellphone networks, where signals will be dropped for everybody who doesn't need mobile access during an emergency.

Again, who is the government to decide who needs service in case of such an emergency.

If they had done what you are suggesting here, then chances are big that we would not have heard what went on in that plane that never made it to its target on sept 11, and the people on that plane would not have been able to interfer with the hijacking.

That there are emergency procedures that ensure communications and other vital resources stay available to those who need it is a cool idea, but the world has become way too complicated for any central government to make the proper choices here, and the only way to ensure vital communications can go on in such a case is by implementing them as independent networks.

Why not just use a modem?

[kaos.geo]

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?

[tmasssey]

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?

[kaos.geo]

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

Re:Why not just use a modem?

[The_Wilschon]

Anyway this chatcord is a nice project for this weekend!! heee! :P

Whoa buddy. Calm down there. Nice, big, easy breaths. Think happy, slow, thoughts. Now give me the mountain dew. Yes, all of it. I'll let you have it back when you're done with the soldering iron.

Re:Why not just use a modem?

[petermgreen]

it could be done phone lines are actually fairly symetrical

however you would have to provide line voltage (about 50Vdc with a high AC impedance) on/off hook detection and ringing yourself

basically you'd be building a minimal phone exchange it could deffinately be done though.

Re:Why not just use a modem?

[tmasssey]

Nobody said it couldn't be done. I've seen lots of devices that let you put two modems together without going through a phone line, and they work just like you said: as a mini exchange.

However, we're talking about the feasability of replacing a $7 cable with a modem. By the time you build your mini exchange, it's gonna cost a little more than the $7 you're trying to avoid spending! :)

Re:Why not just use a modem?

[petermgreen]

if you don't care about on/off hook detection then a lead to work with a modem would probablly be cheaper to make than his. all you need is a power supply (apparently 9V is high enough according to him i find this surprising myself) and a cheap homemade inductor to feed this supply to the line.

you wouldn't need to split the signal with a transformer if you were doing it with a modem and i think the transformer was a significant part of his cost..

Depends on the call

[handy_vandal]

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 ....

-kgj

VOIP is great!

[Cmdr Whackjob]

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!

[2$ Crack Whore]

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 http://testyourvoip.com 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!

[Anonymous Coward]

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

Re:VOIP is great!

[Anonymous Coward]

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!

[Lumpy]

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.

Re:VOIP is great!

[msoori]

I took the VOIP route as well about 1 1/2 years ago. I'm using Packet8 unlimited calling US and Canada for $20 a mnth and have been extremely pleased with it. No more shit from the phone company anymore. Got Road Runner Cable and Packet8 VOIP.

Re:VOIP is great!

[Anonymous Coward]

Actually this is why many companies in Canada and the USA have installed battery backups on their VoIP "modems".
In Canada I believe it's law that they have to provide 911 (emergency) call service even if the "cable" is out.

Re:VOIP is great!

[Anonymous Coward]

Battery backup can do nothing for the cable company screwing up or working on their end of the gear.

IF your cable is fuzzy and your modem loses it's provisioning even a $90,000.00CAD/US APC backup system can not save you.

Simpler (almost cheaper) better looking hack

[Arthur B.]

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

[Anonymous Coward]

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

[NoMoreNicksLeft]

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

[tmasssey]

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.

Re:Simpler (almost cheaper) better looking hack

[RGRistroph]

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

[ShortBeard]

A quick Google and here you go.

Looks real economical.

Re:Simpler (almost cheaper) better looking hack

[Anonymous Coward]

that's $25. On ebay they are $10.

However, that won't let you hook up a regular phone to an asterisk server. It will let you hook up the asterisk server to the line that goes to the phone company. To get a regular phone hooked up to the asterisk, you have either get an IAXy or a cisco ATA 186 or an FXO card. Probably the cisco ATA 186 is the cheapest at around $50 used.

A note about the software

[SuperDuh]

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

[NoMoreNicksLeft]

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.

Re:A note about the software

[greenrom]

Easy. Really easy. It's just a DTMF decoder. If you don't know how DTMF works, see this site for the details. I'd be surprised if there wasn't already some open source software that does DTMF decoding. If not, I would be willing to design a suitable DTMF decoder if someone else wants to write the code to interface it with Skype.

how is this solder free?

[nealrs]

seriously. how?

Re:how is this solder free?

[brakk]

You don't have to solder anything to the circuit board in the phone. The previous article required that.

Warning - USA/Canada is Different

[SirCyn]

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

[pe1rxq]

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.

Jeroen

Re:Warning - USA/Canada is Different

[afidel]

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

[SirCyn]

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

[tmasssey]

Ring voltage can be well over 100V...

Re:Warning - USA/Canada is Different

[SillyNickName4me]

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

[Frank T. Lofaro Jr.]

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).

Re:Warning - USA/Canada is Different

[mikewas]

Those are the most common specs, but they can vary.

Originally the voltage was chosen so that you could pump enough current from the CO (Central Office), out the local loop, through the switch contacts on the phone (close when you lift the reciever), back the local loop, to activate a relay in the CO. This is how the CO knows you want to make a call. If you had customers nearby (you were in the middle of Manhatten) you used 24 V. If you were in a rural area where customers were miles away you used 96 volts.

The ring voltage is a sine wave, with peak-to-peak voltage the same as your DC voltage. Superimposed over the DC then gives you a ring voltage that varies from 0 to twice the DC voltage.

Ring frequency varies. If there's anybody out there with party lines any more, one scheme used different frequencies for each user. The phones' ringers were mechanically tuned to the proper frequency.

Now, switches look for changes in impedance fro mline to ground to detect an off hook. Party lines are pretty much out of the picture, though subscriber carrier systems manage to perform a similar task. But somewhere out there I am sure there is some old equipment still in use. Phone companies don't throw anything away! You often see 60 year old equipment still in use in rural areas.

Re:Warning - USA/Canada is Different

[brakk]

It's not going to ring anyway, so the ringing voltage doesn't matter.

When it's on hook, you're not using it so it doesn't matter what that voltage is either.

I've successfully connected two phones together using a 9v battery, so 9v is enough (don't know about the 5v from USB)

Re:Warning - USA/Canada is Different

[tmasssey]

As a kid, I got in the habit of stripping phone wires with my teeth. 48V hurts, but it's not *that* bad. Just do it quickly and it's OK.

Until the time I got hit by a ring. I've had worse pain, but not by much!

The moral of the story? Don't stick phone wires in your mouth! :)

Re:Warning - USA/Canada is Different

[green1]

I'm a field technician for a large Canadian telco... our equipment does the following:

Ringing voltage: 90VAC @ 20Hz
Talk battery (mostly irrelevant as to on-hook/off hook): 52VDC (drops to 48VDC when the exchange is running on battery backup)
current: minimum 20mA, maximum aprox 50mA
resistances: loop resistance (the resistance of the wire from the line equipment in the exchange all the way out to the customer and back, measured by shorting out the phone jack) is anywhere from 100 ohms or so if you're next door, to around 2000 ohms for very long loops (maximum 1100 ohms if you have ADSL)
resistance of a set on hook: >30Mohm (ideal, some get down as low as about 5Mohm)
resistance of a set off hook: aprox 600ohm

now in the grand scheme of things some of those numbers are largely irrelevant, a 9v battery will operate a telephone (except the ringer) and the switch in the CO will go "off hook" for any resistance from zero up to a couple of k ohms (probably not more than about 3 or 4 k, I know that by the time you get up to about 10 kohm the circuit "mostly" behaves (though it will probably have a "ring trip" (the phone has problems when it rings and goes off hook briefly, enough to "trip" the line)))

Re:Warning - USA/Canada is Different

[SirCyn]

Most Gasoline car engines will run on Kerosene just fine until you punch the gas, and the knock blows the engine. Just because it "usually works" does not mean it's compatible or is meant to work.

Re:Warning - USA/Canada is Different

[SillyNickName4me]

because it "usually works" does not mean it's compatible or is meant to work.

That would apply in the case of the AT&T 5400. In case of the US Robotics modems, they were meant to work.

Also, as others pointed out, the tolerance on the different signalling levels on the phone network is very big, and you may find that both the European and USA implementations fall within those.

The biggest problems for connecting a piece of phone equipment from the USA on a continental European network are:
- needing 220/240V compatible power supply
- for those devices that use pulse dialing still, the pulse length is different.
- The actual dialtone is different (for those devices that care, like modems and faxes)
- The busy tone is different (again, for those devices that care about that at all, and most that do recognize the different variations)

The UK is yet another story.

The signal levels however are not a problem really. I have seen quite a few such devices being damaged due to wrong power supply (or forgetting to set it to 240V) but after 20 years of dealing with phones and modems (my first modem was an imported teletron 1200) I have yet to see one being damaged by the signalling levels being different.

Battery or USB power not necissary

[moroderzone]

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?

[soulhuntre]

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?

[Anonymous Coward]

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?

[enosys]

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.

Re:A common phone recorder will work?

[DavidTC]

Phone line recorders do not have a microphone input, and hence this would not work for this.

Phone line recorders have an output and a trigger line for tape recorders.

Re:A common phone recorder will work?

[Kazoo the Clown]

The Radio Shack phone recorder is output only-- you'd still need a way to hook the phone output to the mike input.

Grammar Nazi

[Anonymous Coward]

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

Re:Grammar Nazi

[nepheles]

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

[ebvwfbw]

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

[blonde rser]

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

[Roger W Moore]

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.

Re:Grammar Nazi

[Anonymous Coward]

The plural of Euro is pounds.

Re:Grammar Nazi

[Anonymous Coward]

Ha. Very nice.

Re:Grammar Nazi

[ebvwfbw]

Wow. This has to be one of the finer examples of constructing a complicated argument just to prove someone wrong.

Complicated argument? Seemed direct to me. The EU consists of many member countries/states. Every one of them with their own ways of doing things (money, government, etc) for centuries and most of them with different languages. When you bind many into one as in a union, it makes sense to look at diplomatic solutions and indeed this seems the simplist way to resolve this question. Deferring to English, you could get into a convoluted argument over what is proper or not and even regional issues. For example in America you would say "20 Dollars", yet in some places in America you would hear "20 Dollar". For that matter, I would "ask you a question" and in some places they "axe you a question".

Anyhow, that is why I chose the way I did. I also left him a way out, maybe they really would say 20 euro in France or maybe he has a valid point. Of course I know they don't say 20 Euro in France, my son having spent Euros recently there (i.e. for the past week). He had many transactions and not one of them said euro, always euros.

Re:Grammar Nazi

[ebvwfbw]

Anyone noted the irony that we don't actually use the euro in England?

Yes, I think most people in Europe and a fair number in the US, Canada and Australia (amoung other places) realize that. Smart actually, at least until 1 Euro == 1 Pound. Then it may make sense to switch, if the Euro is still around by then. Don't worry, they notice. I bet PM Blair gets asked about it every chance by the others.

Re:Grammar Nazi

[rsynnott]

We use the Euro in Ireland (our primary language is English). Most people say 'euro' for the plural; kids tend to say euros.

Re:Grammar Nazi

[nepheles]

You're mixed up in your King Canute reference. King Canute knew the tide would not obey---the point of the exercise was to prove this to his courtiers.

Re:Grammar Nazi

[Kazoo the Clown]

Yeah, well, the plural of email is, uh.. email. The singular of email has become "an email" because ignorant journalists persistently misused the language. "Email" is short for "electronic mail" and we don't use "a mail" to refer to a single piece of snail mail, as the term "mail" is in fact plural. There's no point in fighting it, "an email" is pretty much a done deal. Common (mis)usage trumps standardization. Therefore, if a sufficient number of journalists start referring to "euros" then the English plural of euro may become euros de facto.

The nice thing about standards is that there are so meny of them to choose from. --Andrew S. Tanenbaum

Re:Grammar Nazi

[unitron]

"King Canute knew the tide would not obey..."

Thus proving that his command is pretty much the epitome of futile.

Re:Grammar Nazi

[dbIII]

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

Let it also be known that a euro is a large marsupial with front legs that are stronger than the average kangaroo that is grey in colour. The world is too big and varied to correct peoples grammar or spelling in a global forum - a lot of people reading this will even think I have spelt colour incorrectly because I am not using the US spelling.

The language of a large chunk of the net is broken english - live with it.

Make and accept calls using the buttons?!?!?!?

[Anonymous Coward]

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.

Re:/.'ed?

[Anonymous Coward]

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

solder-free? I think not.

[Ronnie Coote]

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

Ummm

[white1827]

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.

Re:Ummm

[syberdave]

How about us Linux users? I'd like to develop my own software.

Re:Ummm

[register_ax]

To be the happy little dumb consumer all the big corporations like so much only costs $24.95 USD. This solution would cost less at $8.33 USD. For this little savings I might learn something about how the world works and open my mind to creative improvements either to this device or others.

God I hate nerds who don't appreciate hacks; I think it's a "I didn't think of it, so I'll poo on them" kind of thing. Ego is a bitch on the wrong person.

Solder

[Anonymous Coward]

What's wrong with solder anyway?

Re:jew the cord

[fr0dicus]

ich yog zich nit!

No external sound

[RikF]

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

RikF

Re:No external sound

[rubberbando]

Well, you COULD always get an audio splitter or better yet, an audio switcher. :-)

Re:No external sound

[BobPaul]

You can get a USB Mic/Speaker plug:
http://www.usbgear.com/usb-audio-adapter/usb_audio _blaster.html

or just put a stereo mini-pin splitter on your mic and spk out so you can plugin your speakers:
http://www.radioshack.com/product.asp?catalog_name =CTLG&product_id=274-894

(you can get them cheaper than the shack, but it's easy to find there in a pinch)

Re:ok

[Anonymous Coward]

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

Re:/.'ed?

[tomhudson]

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

Busy Tone...

[Anonymous Coward]

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

mod parent up

[enosys]

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

Patent Pending

[pointym5]

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

[ablcmx]

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.

Re:Patent Pending

[ross.w]

Wouldn't something like this violate the test of being obvious? It doesn't really do anything new or novel. I guess in the US that never stopped anyone before, but in the rest of the world (and there is one, you know, at least for now) this might have trouble being accepted for a patent.

Re:Patent Pending

[Anonymous Coward]

Prior Art ?

http://www.nch.com.au/hardware/callrec.html

Its quite close.

Chat cord software is free

[enosys]

The chat cord software is free. Here is a page with information and download links. First you need to login to www.voip-base.com. You can get logins through bugmenot.com. 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.

coincidence!.. and also need help

[Qa32]

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...

FUD

[ImaLamer]

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.

Re:FUD

[waterwingz]

From what I've read, it actually depends on what country you are living in. In the USA, a patent basically blocks even personal use. Actually getting caught is another matter. In much of the rest of the world you can practice what's taught in a patent for educational purposes and scientific investigation.

Re:FUD

[ImaLamer]

In the USA, a patent basically blocks even personal use.

Actually the opposite is true. Patents can't block personal uses.

Re:FUD

[pointym5]

Sorry, but that is not true. Read the patent law: according to 35 U.S.C. 271. (A), anybody who "makes" or "uses" that which is patented is an infringer. Very narrow exception is made by case law when the use is solely for the purpose of understanding the patent.

Pah!

[Zwets]

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

Re:Pah!

[Anonymous Coward]

Is that the real solder free version?

What's the Point?

[dbucowboy]

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

Re:What's the Point?

[Eric604]

No.

Re:What's the Point?

[dbucowboy]

ok.

Re:jew the cord

[Anonymous Coward]

Jews did wtc

Son of the Grammar Nazi

[bwcbwc]

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.

Why draw the line at half-assed?

[Anonymous Coward]

When you can get an Handytone http://www.grandstream.com/y-htseries.htm/ or IAXy http://www.digium.com/index.php?menu=product_detai 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 suck......it is skype right? Or is it only lame when proprietary isn't free?

Re:Why draw the line at half-assed?

[Anonymous Coward]

Well, both sites quote the price as $404, so comparing to 7 Euro, that sounds rather expensive...

Whattofix.com link is now a story on /.

[screwthemoderators]

http://science.slashdot.org/article.pl?sid=05/07/0 5/1422222&tid=133&tid=160

Acutally - no.

[Anonymous Coward]

It's pretty fast from my place in southern Europe.
Maybe it's the transatlantic cable that is slashdotted?

Isn't it time just to put a link to hackaday?

[Lawrence_Bird]

just about everything in this category ends up having been
posted to hackaday.com a week earlier. Time to redirect
the category to their site.

Re:coincidence!.. and also need help

[Anonymous Coward]

The 1-800 numbers to corporate "customer support" lines are cheap because they are VoIP all the way to the end of the line. It never uses the foreign country's telephone system.

On the other hand, when you go to call someone who is NOT in a call center in India, the call has to go over the POTS or cell phone network. In most of those countries even local calls are not free.

Linux anyone??

[pair-a-noyd]

I see the program is for windows only.
Has anyone found a way to do this with skype for linux?

Priorities

[Dareth]

A cell phone is not a necessity despite what many people think.

Necessities are food, water, and shelter.

Many people in this world do not have these basic things.

Though some of them might own a cell phone anyway.

Re:Priorities

[dbucowboy]

True, however, most people that are buying/making Chat-Cords and have broadband internet aren't lacking in the food, water, and shelter categories. I would venture to say that 90%+ of people that have high speed internet also have a cell phone. These are the people I was referring to when I said everyone in the world. Obviously the invisible children in the Sudan don't have cell phones.

What about the mobile version?

[nuckfuts]

I'd love to find a DIY version of this cable that connects a cell phone to Skype:

http://www.ipdrum.com/default.aspx?m=4

Such a cable would enable "free" cell phone calls as described here:

http://www.pbs.org/cringely/pulpit/pulpit20050623. html

Free Skype-Out?

[n01]

How about writing a Skype to SIP gateway. That's because of an offer of 1und1.de of a calling 'flatrate' for around 10/month to any landline in Germany.

If I had such a gateway, I would offer people free calls to numbers in Germany, maybe asking them for a small donation if they use it a lot, so I can cover my expenses.

However, I didn't find any OS or free (as in beer) configurable SIP client to connect this to... I've looked a bit into the Skype API, and it seems connecting to Skype should work (one problem being that Skype needs to connect to a soundcard, so I would also need a 'virtual' soundcard, if I don't want to connect two soundcards together) or connect the phone line to the soundcard (my modem/router handles the SIP translation), which probably could be done with a device similar as the one presented in the arrticle.

What do you think of this idea, would you place a call through a Skype-SIP-PSTN gateway (privacy implications...)?

Maybe you know of a solution already?

Kind Regards,
Florian

Re:Free Skype-Out?

[Vo0k]

One problem:
One person at a time. They would have to wait in queue for the connection, and your own line would be busy 99% of the time.

Caller ID?

[blindseer]

Bonus points for people that get Caller ID to work over this interface.

Software Patent

[BobPaul]

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.

There's way too much prior art on something like this for them to get a patent. It'd be almost like trying to patent the telephone or the 600 Ohm 1:1 transformer or something.

If anything, they are going to patent the software and/or the solution as a whole so that you would only be infringing if you sold a product identical marketed for VOIP use, since that's the only somewhat novel thing they did.

In any event, note that their patent is PENDING, not granted. I wouldn't worry. (or care... just don't sell your home made ones)
--
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