http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/ Engadget Comments for How-To Build a Telephone Recording Circuit from an Old Modem http://www.engadget.com/media/feedlogo.gif http://www.engadget.com en-us Copyright 2008 Weblogs, Inc. The contents of this feed are available for non-commercial use only. Blogsmith http://www.blogsmith.com/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
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]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
Either way, my description of the simpler method for achiving what they described will work for you.

-TAZ]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=43-228
Plkug it in to your sound card and you are reday to go.]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
What they describe would be closer to a phone tap as it can be easily concealled, what I described would be siting out in front of you for recording conversations as was described as the intent.

But for that matter, you can get this type of tap for about $5 (do a search on 'phone tap')

If you ask me this wasn't worthy of an Engadget Do It Yourself posting

TAZ]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/what's a good, cheap, low-powered recording device to couple with this? perhaps we need a DIY flash recorder posting...

i've got a box full of 28.8 pci modems in my garage. i bet all you DIY-haters would pay $20 for one of these on ebay.]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
http://dmcex.com/more/pdfs/osti_8-1000_plans.pdf]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/

Most modems use high voltage caps to prevent DC current from passing through the transformer, this cap should probably also be scavenged for the circuit. (You want to block the hook current through the transformer because otherwise it gets ever so slightly warm over time, which can screw up it's characteristics enough to need to re-sync the echo cancellation in a modem. Most modems use a semiconductor circuit to carry the off-hook current.)

I wouldn't leave this circuit connected to my audio rig in a thunderstorm either...



]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
If there's a way to plug in all those components directly on the modem's board, it would probably be better since all the necessary circuits are already installed and have proper routing.]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
http://www.tkk.fi/Misc/Electronics/circuits/teleinterface.html#networkint]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/It means that upwards of 200V may be applied across the phone tap circuit here. The image above shows two 10uF 35V caps being used. Not only are these polarity sensitive, they have a maximum working voltage (as marked 35V DC) that should not be exceeded. They can leak, or even explode. Please, if anyone builds this circuit, use decent parts and get at least 200V caps. Given the signal levels and frequencies, 10uF is overkill. A 0.1uF 200V ceramic capacitor would be more than sufficient, as well as much safer.
A simple google search provides more information on POTS interfaces.]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/If I hang my phone up.. does this circuit hangup too? What if we wanted to take this a step further and make it voice activated?
]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
2. Those are only rated for 35 volts .... anyone with POTS experience knows a ring signal could easily be over 200V, not to mention spikes and surges.

These things almost surely add up to an explosion at some point in time. What you need to use is a HV (high-voltage) ceramic capacitor rated for no less than 1000V.

Please, take my word for it. I know all too well what it takes to make a phone interface. I don't want to see any would be phreakers lose an eye over something as silly and obvious as this.]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/

Most modems use high voltage caps to prevent DC current from passing through the transformer, this cap should probably also be scavenged for the circuit. (You want to block the hook current through the transformer because otherwise it gets ever so slightly warm over time, which can screw up it's characteristics enough to need to re-sync the echo cancellation in a modem. Most modems use a semiconductor circuit to carry the off-hook current.)

I wouldn't leave this circuit connected to my audio rig in a thunderstorm either...



]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/lesson: choose your capacitors wisely. and wear safety glasses when you're doing anything more dangerous than reading a book.]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Hey, I'm building this circut right now. I have all the things saudered down to the board... but now I have no idea which side is positive and negative...

I need to know which pins are which P/N for the
-Telephone Jack
-Mini jack

Can't really continue until someone answers :P
Thanks!]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
http://www.concelsys.com/voice_modem_software_call_recorder_logger_apr.htm]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
the phone jack was a little harder to find a schematic on the connections, but looking at it when the clip on the bottom, pin 1 is ground, then recieve, then transmit, then power. I'm still kind of fuzzy on what's + and - in this project, but you only need the middle two pins.
]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/
what do they look like?]]>Dec 19th 2005 2:47AMhttp://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/http://www.engadget.com/2005/09/27/how-to-build-a-telephone-recording-circuit-from-an-old-modem/Dec 22nd 2005 10:28PM