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Old October 30th, 2008, 06:37 AM   #1
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Recording Telephone Conversations

In this thread it is assumed that all conversations recorded from a telephone are with the knowledge and consent of all parties - anything else could result in breaking the law, depending on which country you are in.

Just what is the state of play now, technically, in recording phone conversations? The simplest way is to tape a tram or other personal mic to the ear piece of the handset. Good for separation of voices, bad for rustle as mic is pressed against listener's ear. You can make up a circuit involving a 600 ohm transformer, which is necessary to stop the up to 50 volts DC on a subscriber line from going to your input. This too may have legal implications as to connect an unapproved device directly to a telephone circuit is resented by most telecomm companies. Also, with this method the voice of the person whose phone line you are using will be much louder than the person at the other end - although in post production this can be laundered, especially if you are recording the speaker on a mic on another channel.
I have seen devices advertised which presumably work by induction, where they are clamped round a phone line - don't know how well these work. In-ear mics too I have seen, but I suspect that they may suffer from rustle. Sticking a personal on the earpiece of an extension phone works, but again the levels are uneven. Technically, companies using phone-ins have expensive TBUs (telephone balancing units) which match the impedance of each phone line and reverse the phase of the speaker's voice to reduce its level, much in the way that old phones used to (but not completely so that you get side tone, a little bit of your own voice in your ear).

So what do all you guys do? Have I missed out a good method?
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Old October 30th, 2008, 07:31 AM   #2
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Nick... You appear to have a better technical grasp of the issues than I, and there are different rules with different countries/companies, but I think you might be overtaking the plumbing a bit.

Here in the colonies, phone device vendors (V-tech, Panasonic, et al) have long been selling phones (mostly cordless) with integrated earphone jacks. A simple cable is all that's required to connect it to your preferred recording device. That's the rough and tough way to do it.

On the other end of the spectrum, there have long been specialized devices to record the telephone conversations and I really don't know the state of the current art there. They are likely on the pointy end of the price/value spectrum.

I may be overly simplistic here but since the audio bandwidth of telephone lines is so limited, I would think that the goal would be to capture what quality exists whilst mitigating the noise. Anything beyond that would depend upon your use case.
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Old October 30th, 2008, 07:32 AM   #3
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Down at The Bill we used to do any ADR needed for RT reverses over the phone!

Yup Over the Phone! as it was due to be fuzzed anyway it was acceptable to record the voice over the phone line if the actor wasnt on call and at home.

We had an old dial type telephone with an XLR output from the earpiece and a switch on the side to select either the earpiece or to re-direct it to the XLR output. It also muted the voice microphone too.

Very Very Heath robinson but no tele balance units and a really simple way of doing it as you could talk to the artist over the phone receiver and then just flick the switch when you needed to record the telephone output.
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Old October 30th, 2008, 07:52 AM   #4
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The best way to go is with a device called a "phone patch" or a "phone tap." Here's a link to a Rane Note discussion of the principles and a schematic for a DIY version - Interfacing Audio and POTS. You can get commercial versions for not too much money from broadcast supply houses. A Google search will turn up lots of references. Here's a commercial example ... http://www.jkaudio.com/inline-patch.htm or http://www.pro-sound.com/M1/SPSCPTAP.html
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Old October 30th, 2008, 08:57 AM   #5
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Finally, a topic on this board where I can be helpful. As far as I know, the best way to record phone conversations is actually through Skype, or possibly another internet-based program that allows you to talk to other people. You can then use a program to record the conversations. I use Powergramo. I also tried Hot Recorder. That didn't work for me although it's supposed to be good. There are a lot of different programs to do this, different ones for PCs and Macs.

There's something about the lines that they use over the internet that are better versus land lines. I heard a brief explanation about it once, and it was something like the internet uses digital cable or lines to connect things, so you can reduce background noise better.

Here's an in-depth conversation about it:

http://www.blogarithms.com/index.php...or-interviews/

Basically, Skype is free. You can call any phone in the world with it, and from what I've heard it produces better quality than the other ways.
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Old October 30th, 2008, 10:14 AM   #6
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We had a well known author come to us with this problem. They were getting horrible results recording phone conversations and wanted something really clean. I wanted to put together a simple solution since they were a bit "technically challenged." I went with Steve's suggested solution, the JK Audio QuickTap. The company also makes a "Cell tap" and a few other higher end devices.

Now, to truly be helpful to this big name, I wanted to make sure they knew all the steps involved and didn't make any mistakes. At the time the Edirol R-09 was the best portable recorder on the market, so I turned on the camera and recorded a short video showing them how all the components were connected. The Edirol R-09, the QuickTap and the typical office phone. If you're interested, you can watch the video on YouTube - Edirol R-09 with QuickTap for Phone Recording
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Old October 30th, 2008, 11:03 AM   #7
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I've done lots of work with phone patchs, aka digitial hybrids, from Telos, Gentner and JKL. They all work very well. However, they record what's available on a telephone line

I agree with Joshua 110% in what he wrote above. The quality of a skype recording, when properly set up with usb headsets on both ends, is outstanding and the connectivity is free. Recording software about $20-$40, usb headsets about $40-80.

I used the info in the link Joshua provided, and I'm very happy with the results, having done about 40 recordings this way. I used Pamela on the pc, but I think if I did it again I'd try Total Recorder.
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Old October 30th, 2008, 11:06 AM   #8
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As usual this site has provided me with a full answer and many useful leads. Steve, thanks for the link to Interfacing Audio and POTS, a fascinating article that reminded me about the joys of hybrid transformers. Thanks a lot guys for all your help. I'll be down to Maplins for the parts and soldering up a storm over the weekend!

By the way, are there any mobile phones (cell phones) that have a jack for recording?

Last edited by Nick Flowers; October 30th, 2008 at 11:12 AM. Reason: New thought occurred.
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Old October 30th, 2008, 11:17 AM   #9
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I needed to record over-the-phone interviews for podcasts and bought a digital hybrid unit from JK Audio and it worked fine, but it is expensive.

An answering machine with a tape and unlimited recording can be used to record a call. I used to do this.
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Old October 30th, 2008, 11:59 AM   #10
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Quote:
Originally Posted by Nick Flowers View Post
As usual this site has provided me with a full answer and many useful leads. Steve, thanks for the link to Interfacing Audio and POTS, a fascinating article that reminded me about the joys of hybrid transformers. Thanks a lot guys for all your help. I'll be down to Maplins for the parts and soldering up a storm over the weekend!

By the way, are there any mobile phones (cell phones) that have a jack for recording?
Not dedicated record outputs but you can bodge a hands free kit to do it!

We used to use cell phones as four wire comms units back in the late 80's where BT couldnt get a line in.
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Old October 30th, 2008, 12:13 PM   #11
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EEC Regulations

I've noticed that the In Line Patch, sold by JK in nearly every country and seemingly EXACTLY what I want, is not on their list of devices approved for use in the EU. Can this be the Dead Hand of Brussels thwarting us in the UK again?
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Old October 30th, 2008, 12:44 PM   #12
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Quote:
Originally Posted by Nick Flowers View Post
I've noticed that the In Line Patch, sold by JK in nearly every country and seemingly EXACTLY what I want, is not on their list of devices approved for use in the EU. Can this be the Dead Hand of Brussels thwarting us in the UK again?
JK Audio has been very responsive in the past. If you email them with your situation and what you want to do (and location), I expect they will tell you what options they have for you. They will also tell you which is best, next, etc.
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Old October 30th, 2008, 01:03 PM   #13
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Quote:
Originally Posted by Nick Flowers View Post
I've noticed that the In Line Patch, sold by JK in nearly every country and seemingly EXACTLY what I want, is not on their list of devices approved for use in the EU. Can this be the Dead Hand of Brussels thwarting us in the UK again?
More like BT keeping their monopoly on comms in the UK, they dont bother to upgrade their networks but are happy to take the for crap service.

We had a BT service bod around once and he took great delight in trying to fine us for our faulty equipment causing a line problem. When I told him I was ex broadcast and actually stated where the fault would be and what it was he left with his tail in his hand. They still sent us a bill though and we had to then fight the indian service line to get satisfaction.
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Old October 30th, 2008, 01:10 PM   #14
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The way high-quality phone interviews are done in the U.S. is to employ a ISDN line.

Here's a UK source of information: Corporate ISDN Codec Radio Interview Systems ISDNAUDIO.COM Corporate Solutions
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Old October 30th, 2008, 01:43 PM   #15
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Digression to berate BT

Sure, ISDN for good quality is the way to go. Most of my work needing phone taps though is for consumer programmes and regional news using real people and their own phones.

Don't start me on BT, Gary! They actually publicly stated that broadband would never, ever come to our phone exchange, let alone my house. This was after they dug up eight miles of roadside trench to lay fibre optics to that same exchange for an emergency services radio network- but as that was a privately paid job, they didn't think to lay in an extra line for Joe Public to use. So I had to lay out a lot of bucks to install a microwave link over the hills to Portsmouth exchange (a co operative effort with the other villagers -Lord, that sounds like pitchforks and flaming torches) a 25 mile relay. The upside is that I now get 7 Megs!
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