Build Your Own Chat-Cord 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."
Google Cache (Score:5, Informative)
article text for those who are /.ed (Score:4, Informative)
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 (Score:5, Interesting)
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 (Score:2)
Would you have some links that illustrate what you're talking about? A
Re:article text for those who are /.ed (Score:2)
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 an
Re:article text for those who are /.ed (Score:2)
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 (Score:2, Informative)
This Sounds Like A Good Cottage Industry (Score:4, Interesting)
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 [whattofix.com]
Re:This Sounds Like A Good Cottage Industry (Score:1)
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 (Score:1)
Re:This Sounds Like A Good Cottage Industry (Score:2)
Re:This Sounds Like A Good Cottage Industry (Score:2, Interesting)
Re:This Sounds Like A Good Cottage Industry (Score:2)
Such things are better left for fun and amusement [abrij.org].
Re:This Sounds Like A Good Cottage Industry (Score:2)
Every story in Hardware Hacking [slashdot.org] 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.
Erm (Score:5, Informative)
Re:Erm (Score:2)
Re:Erm (Score:2, Informative)
Tis great, but... (Score:1)
Depends on the call (Score:3, Funny)
Depends on the nature of the call -- in some cases, I only need one free hand
-kgj
Why not just use a modem? (Score:1)
Re:Why not just use a modem? (Score:3, Insightful)
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? (Score:1)
Re:Why not just use a modem? (Score:2)
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? (Score:2)
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..
Re:Why not just use a modem? (Score:2, Funny)
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.
Simpler (almost cheaper) better looking hack (Score:1)
Re:Simpler (almost cheaper) better looking hack (Score:3, Informative)
Re:Simpler (almost cheaper) better looking hack (Score:2)
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 th
Re:Simpler (almost cheaper) better looking hack (Score:2)
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
A note about the software (Score:1)
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 (Score:4, Informative)
Re:A note about the software (Score:2)
Warning - USA/Canada is Different (Score:5, Informative)
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 (Score:3, Informative)
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 (Score:2)
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 (Score:2)
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 s
Re:Warning - USA/Canada is Different (Score:2)
Re:Warning - USA/Canada is Different (Score:2)
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 22
Re:Warning - USA/Canada is Different (Score:2)
Re:Warning - USA/Canada is Different (Score:1)
Re:Warning - USA/Canada is Different (Score:2)
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 (Score:4, Informative)
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.
Battery or USB power not necissary (Score:1)
A common phone recorder will work? (Score:1)
"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 [radioshack.com] 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? (Score:1, Interesting)
Re:A common phone recorder will work? (Score:2, Informative)
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? (Score:2)
Grammar Nazi (Score:1, Interesting)
Re:Grammar Nazi (Score:5, Informative)
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 [eu.int] published by the EU clarifies things.
Re:Grammar Nazi (Score:1)
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 (Score:2)
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 (Score:2)
Re:Grammar Nazi (Score:2)
Re:Grammar Nazi (Score:2)
Thus proving that his command is pretty much the epitome of futile.
Re:Grammar Nazi (Score:2)
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
Re:Grammar Nazi (Score:2)
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.
Ummm (Score:5, Insightful)
mod parent up (Score:1)
Chat cord software is free (Score:2)
Alternatively, here are direct links to the files: DialerXT [voip-base.com] and DialerSK (for Skype) [voip-base.com]. I'm not sure if these would work for everyone. I'm including them because this way would be much simpler.
Re:Ummm (Score:2)
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.
No external sound (Score:2, Informative)
Re:No external sound (Score:2)
Re:No external sound (Score:2)
http://www.usbgear.com/usb-audio-adapter/usb_audi o _blaster.html [usbgear.com]
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 [radioshack.com]
(you can get them cheaper than the shack, but it's easy to find there in a pinch)
Patent Pending (Score:2)
Re:Patent Pending (Score:1)
FUD (Score:2)
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 (Score:2)
Re:FUD (Score:2)
Actually the opposite is true. Patents can't block personal uses.
Re:Patent Pending (Score:2)
Software Patent (Score:2)
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
Pah! (Score:3, Funny)
What's the Point? (Score:1)
Priorities (Score:2)
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.
Isn't it time just to put a link to hackaday? (Score:4, Informative)
posted to hackaday.com a week earlier. Time to redirect
the category to their site.
Linux anyone?? (Score:2)
Has anyone found a way to do this with skype for linux?
What about the mobile version? (Score:2, Interesting)
http://www.ipdrum.com/default.aspx?m=4 [ipdrum.com]
Such a cable would enable "free" cell phone calls as described here:
http://www.pbs.org/cringely/pulpit/pulpit20050623
Re:ok (Score:1)
Or maybe the site is hosted via a line using this phonce cord?
Re:ok (Score:2)
(Whoa cowboy! You must have more than two fingers. Please chop the extra ones off, and repost)
Re:VOIP is great! (Score:2, Informative)
Anyway, you can test your VoIP quality from anywhere with IP and a Java-enabled browser at http://testyourvoip.com [testyourvoip.com] if you are concerned about your IP quality not being up to snuff, or if you want to see how
Re:VOIP is great! (Score:2)
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
Re:WHY???? (Score:1)
Re:WHY???? (Score:1)
Re:WHY???? (Score:2)
Re:WHY???? (Score:1)
Re:WHY???? (Score:2)
Re:WHY???? (Score:2)
Re:WHY???? (Score:1)
Re:WHY???? (Score:2)
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 combine
Re:WHY???? (Score:2)
Somehow the IP network seems to be more resistent to partial failure then the phone network.
Re:WHY???? (Score:2)
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
Re:WHY???? (Score:2)
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???? (Score:2)
There's a lot happening with packet based voice communications, and much of it is centerred around Quality of Service.
Re:WHY???? (Score:2)
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 cl
Re:WHY???? (Score:2)
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
Re:WHY???? (Score:2)
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 emergen
Re:WHY???? (Score:2)
Re:/.'ed? (Score:2)
Re:/.'ed? (Score:1, Funny)
Re:jew the cord (Score:1, Offtopic)
Re:Free Skype-Out? (Score:2)
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.