VoIP hardware hacking: the cheap telephone to computer soundcard adapter
Since at least the year 2000, I've been looking for a solution to the "how do I plug my phone into my computer" question. Several products have seemed to be moving too slowly toward a price point I'd've bought. I think the original idea was to use a real phone to make calls through the then-free Dialpad service.
Oh, sure, I've tinkered with hardware. I've got a pair of Creative Labs (supposedly, though it appears they were just repackaged Innosphere devices) VoIP Blasters I bought for $20+s/h, after Creative decided to dump inventory, just before the slashdot article that made them scarce. Of course, that's a fairly nice piece of hardware, with cruddy software (and, though there are open-source replacements, the built-in irrevocable g.723.1 codec is, well, a pain), and, consequently, has gotten almost no use.
After the VoipBlasters, I watched several line-level to phone adapter devices go by, often costing $80 or more. Just wasn't worth it.
Last year, when I really getting into VoIP, I picked up some good standalone hardware, a Sipura (now Linksys) SPA-2000, and later a SPA-3000. Those are great boxes, but they don't let you plug a phone into your computer directly, meaning, if you want to interact with software-only tools (like reigning champ Skype) you'd have to deal with a lot of hacks, or control a lot of the pathway to the other side.
Finally, enough hobbyists were getting into this stuff that I started seeing explanations of how to build the thing yourself. In particular, a company has put together a fairly cheap solution already, and, since they didn't have the software done when the put the product on the market, it's now widely used by people who home-build the same thing, meaning that you could build such a device and have it be more than just a telephone-shaped headset, but actually interact in the call generation (the Chat-Chord software even generates dialtone, er, sometimes...). I decided to give one of them a shot, the Grynx tutorial sounded easy enough. I ordered the parts, but, when they got here, it turned out that for one critical centerpiece, a phone-specific transformer, I had ordered not quite the right thing. Whoops.
Then, eureka, another tutorial came along. This one didn't appear to use any hard-to-find components, just a pile of resisters and capacitors. I dropped by Rad Shack on the way home tonight, and picked up what I still needed (I already had the female RJ11, and the 1/8" computer wires, cut from an old broken headset), and sat down to breadboard things together.
Amazingly, I wasn't missing any parts, and things went together pretty straightforwardly.... I bought too many resisters, and I'd bought a grab bag of potentiometers and capacitors, so I had to do some tinkering and measuring. Once I found the bits, and put them all together, I plugged it into my computer, plugged in a phone, and, without further ado, I had recording. Sound levels seemed fine, too. I thought I'd broken the line return part of the circuit, but then I checked my wires, and found I'd plugged the line return into the wrong plug on my computer.
Bottom line: It works! Here's a pic:
... now, to not break it while transferring it from breadboard to a case. I'm thinking an Altoids case, since that seems to be a popular trick lately. Anyone got an extra spare one?
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