How-To Build a Telephone Recording Circuit from an Old Modem

posted Sep 27th 2005 3:03am by fabienneserriere
filed under: Uncategorized

modemmatte2

We’ve posted our How-To for the week over at Engadget. Do you have an old modem lying around? Have you been dying to record some of your phone conversations for those podcasts or homebrewed movies or crazy flash animations you make? Wait no longer! Build yourself a little circuit to change the analog phone’s audio to regular line audio to record with your sound card. Remember that it is illegal in many places in the world to record phone conversations without both parties’ consent.

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Comments [19]

Reader Comments

Wow! great and easy hack! I

Posted at 3:28 pm on Sep 27th, 2005 by william

The next part of this project should be making it wireless so that you dont have that nasty 3rd wire. also you could tap a phone like that…

Posted at 3:50 pm on Sep 27th, 2005 by bird603568

I just built one of these, works pretty well.
Only problem is you have to speak quite loudly and clearly into the phone to be heard; otherwise it gets buried under a fairly loud medium-pitched drone (nothing to do with the phone itself). Could it be because I used 22uF caps instead of 10uF?
Awesome hack, either way, and questionably legal.

Posted at 7:00 pm on Sep 27th, 2005 by Alex

That should work great… I am an armature sound technician and run nice sound system. Now I will now be able to run a phone conversation through my sound system.

The next step for me would be to run the mix from the mixer minus the phone call (eliminate feedback) back to the person on the phone. Any ideas?

Posted at 7:16 pm on Sep 27th, 2005 by Jon

That should work great… I am an armature sound technician and run nice sound system. Now I will now be able to run a phone conversation through my sound system.

The next step for me would be to run the mix from the mixer minus the phone call (eliminate feedback) back to the person on the phone. Any ideas?

Posted at 7:16 pm on Sep 27th, 2005 by Jon

you could hook it up to a simple AM transmitter (construction instructions here: http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html) and have it transmit to a radio attached to your computer. simple cordless wiretap.

Posted at 7:17 pm on Sep 27th, 2005 by adam

hey i think this is very cool hack with or without a few extra wires. what else are you going to do with an old obsolete modem. im gonna try it out.

Posted at 9:05 pm on Sep 27th, 2005 by chris

hey i think this is very cool hack with or without a few extra wires. what else are you going to do with an old obsolete modem. im gonna try it out.

Posted at 9:30 pm on Sep 27th, 2005 by chris

Sorry to be a downer, but the capacitors are only rated at 35 working volts, and polarized. The 100 volt ring signal from the phone company may destroy them, best to use non-polarized with telephone circuits as well.

Posted at 11:39 pm on Sep 27th, 2005 by mhall

six or seven years ago i did something pretty similar in order to wire my laptop modem to a cordless phone headset jack. it worked, i got all the way up to a blistering 14,400!

Posted at 12:45 am on Sep 28th, 2005 by mac

You guys should really be careful with this. Most states have very strict wiretapping laws.

If you record someone without their consent, you could go to jail or face a civil suit.

The following states require the consent
of ALL parties before being allowed to record:

California, Connecticut, Florida, Illinois, Maryland, Massachusetts, Michigan, Montana, Nevada, New Hampshire, Pennsylvania, Washington.

http://www.rcfp.org/taping/quick.html

Posted at 9:22 am on Sep 28th, 2005 by Chris

oh.. p.s.. playing stupid won’t get anyone out of trouble either..

So.. if you live in one of those states and you happen to record your phone s*x or break-up with your girlfriend, the unsuspecting person on the other line could make your life difficult.

Posted at 9:25 am on Sep 28th, 2005 by Chris

Hey chris. You just sensored the word SEX. What are you, 8?

Posted at 7:31 pm on Sep 28th, 2005 by windwaker

could this be used as a line out? Like if I wanted to play a song off my iPod to my friend on the other end of a conversation, would that work?

Posted at 11:24 pm on Sep 28th, 2005 by John

John – it’s definitely possible, but not with this setup. (As written) gives audio line out.

Now, here at HAD, we pride ourselves on not doing things as written, don’t we.

Posted at 1:01 am on Sep 29th, 2005 by Dave Alexander

You could also do this with a couple of RCA jacks , a couple of SPDT switches and a 600:600 transformer.

Much easier, good signal and you dont have to wreck a modem to do it.

http://www.phreaksandgeeks.com/boxes/meeko.txt

Posted at 11:26 am on Oct 7th, 2005 by Allan

This was my first electronics project… The schematic sucked and I’d never soldered before (except messing up my xbox, heh. I got it fixed by a friend). My dad helped me out with it, and we spent a few hours on it last night. It didn’t work. :( then, looking at it today, there was no continuity through the transformer. I just replaced it and it still didn’t work. Then I noticed I used a 100 uF Capacitor instead of 10 for one of them. It worked!!!

Posted at 5:28 pm on Oct 29th, 2005 by gaarie

Hey Allan,

it seems like that Meeko box does not have any schematics available. Can you send them to me please, it seems like exactly what I want to build. My email address is sebs89 _at_ gmail d0t com. Thanks in advance!

Posted at 10:13 am on Mar 17th, 2006 by SeBsZ

I was wondering about this unit…
Will it automatically pick up a phone call, or do you have to start or switch something on when the phone is picked up??
Thanks for the info in advance.

Steve

Posted at 2:38 pm on Apr 20th, 2006 by Steve