iPhone Call Recorder

by Adam on August 20, 2009

UPDATE: There is a better way to record calls on your iPhone or any other Bluetooh enabled phone – Check out my review of the Call Mynah.

8/26/2009 – I have seen some comments around some forums that this device is illegal. It’s not. It’s perfectly legal to make a device that enables you record phone calls and it’s perfectly legal to record phone calls to which you are a party of. However, depending on your jurisdiction, you may have to notify the other party that the call is being recorded. It’s always illegal to record a phone call to which you are not a party. Your mileage may vary, when in doubt do some reading, and consult a lawyer.

The Problem

UPDATE: There is a better way to record calls on your iPhone or any other Bluetooh enabled phone – Check out my review of the Call Mynah.

I’ve wanted a way to record phone calls to and from my iPhone since I’ve had it but hadn’t really looked into solutions until a couple of weeks ago. What I really wanted was a native iPhone app that would record incoming and outgoing phone calls – there is SpoofApp but it requires a JailBroken phone, per-minute fees, and looks like it only works on outgoing calls. Another iPhone app Recorder 10, does not require a JailBroken phone but like SpoofApp you have to pay per-minute fees and it only records outgoing calls.

Exhausted after searching for something I assumed would be out there already, and finding nothing I figured that the only way I was going to get what I wanted was to do it myself.

I had a few criteria that I wanted to meet:

  • Portable as possible.
  • Record both sides of the conversation.
  • The ability to start recording the conversation midstream.
  • As little indication that the call was being recorded as possible.

Before I go any further – laws regarding the recording of phone calls vary from state to state and federal laws may apply as well. Don’t be stupid, do some reading and if in doubt talk to a lawyer. If you make this device and get yourself into trouble using it I’m not responsible. I’m also not responsible if you release the magic smoke from your iPhone.

The Obvious Solution

UPDATE: There is a better way to record calls on your iPhone or any other Bluetooh enabled phone – Check out my review of the Call Mynah.


When you talk on a phone, whether you notice it or not, you hear a smidgen of your voice through the phones speaker. If phones didn’t do this it would sound strange when you talked on the phone. So my first test was to just record the headphone output [using a splitter] of the iPhone to see if I got both sides of the conversation. You can record both sides of the conversation like this but the iPhone side of the conversation is unacceptability low.

This is the method used by Rory but he uses the built in microphone on his Mac to record his side of the conversation. So, while Rory has a workable solution it requires the use of a computer so it’s not all that portable.

8/25/2009 – Previously I incorrectly stated that this method causes an echo on the recording but after going back and trying it last night I could not replicate this effect; go figure.

With this method you’re relying on the smidgen of audio that the phone feeds back to your ear piece. This is not enough to get a decent recording of your side of the conversation, which is why Rory uses his Mac's mic to record his side of the conversation.

With this method you’re relying on the smidgen of audio that the phone feeds back to your ear piece. This is not enough to get a decent recording of your side of the conversation, which is why Rory uses his Mac's mic to record his side of the conversation.

Without using a second recorder (in Rory’s case his Mac) for your side of the conversation using this method your recording sounds like this. Notice you can barely hear my side (iPhone side) of the conversation and when it gets loud, you can’t hear my side at all.

A Better Way

UPDATE: There is a better way to record calls on your iPhone or any other Bluetooh enabled phone – Check out my review of the Call Mynah.

So, I started to look at the pinout of the iPhone headphone jack which is a TRRS (Tip, Ring, Ring, Sleeve) jack. I stumbled across this post that gave instructions on how to wire a breakout cable so that you could use your own headphones and mic with the iPhone and after some dabbling I came up with this:

In this schematic the W, R, Y and NS (White, Red, Yellow, and Not Shielded) note the color of the individual wires for the TRRS cable I used.

In this schematic the W, R, Y and NS (White, Red, Yellow, and Not Shielded) note the color of the individual wires for the TRRS cable I used.

Which, if you haven’t guessed already, does not work. Well, It actually does work. It records both sides of the conversation beautifully. The problem is that the person your talking to hears everything they say repeated back to them (delayed by a millisecond) in their ear peace, very loudly and very clearly. Not only would this “talk back” be very annoying for the person your talking to, it would defiantly indicate to them that something odd was going on with the call.

It seems obvious now but it took me awhile to figure out what was going on – to get the recorder to work the way I wanted, I needed to combine the headphone output and the mic input (my side of the conversation), to one single output that would go to the recorder. By doing this I ended up feeding the headphone output of the iPhone back into the mic input of the iPhone, which is why the person on the other end heard everything they said repeated back to them. The obvious solution was to not combine the headphone and mic to one output, but to record the calls I’d either need two recorders (one for each side of the conversation) or a recorder that had multiple inputs. I wanted to get it working using only one recording output.

I wondered if using a mixer would solve the problem and to test this I connected the headphone and mic outputs to my little Behringer mixer on separate channels and it worked beautifully. Unfortunately, as beautifully as it worked, it required the use of a small but not so portable mixer. So I consulted Google and found some schematics (link 1, link 2) for some simple two channel mixers. However, using simple mixer did not do enough to keep the headphone and mic separated, it helped but it wasn’t enough. Finally, by using strategically placed capacitors I was able to virtually eliminate the “talk back”problem.

The Solution

UPDATE: There is a better way to record calls on your iPhone or any other Bluetooh enabled phone – Check out my review of the Call Mynah.

Record iPhone Calls | iPhone Call Recorder


To keep things simple I combined the left and right headphone channels [see: Stereo-to-Mono Summing Box] to make a mono signal going to the recording output but the headphone output for the iPhone user (you) is still stereo. Also, you could probably use lower resistor values all around since the signal coming from the iPhone isn’t that hot but I decided to err on the side of caution for now. The potentiometers are your garden variety (Radio Shack) 100k audio taper pots; you could use 50k or probably even smaller with this setup and they only control the signal going to the recording output, which gives you some control of the recording levels.

Depending on the headset you use, you may need to modify the cable to have the headphones and mic on separate jacks; the one pictured here was made with separate headphone and mic jacks. Here I have the iPhone Call Recorder hooked up to a hand held voice recorder (which has a mic input) but you could use any recording device that accepts a 3.5mm jack.

Depending on the headset you use, you may need to modify the cable to have the headphones and mic on separate jacks; the one pictured here was made with separate headphone and mic jacks. Here I have the iPhone Call Recorder hooked up to a hand held voice recorder (which has a mic input) but you could use any recording device that accepts a 3.5mm jack.

Click here to listen to a phone call recorded using the iPhone Call Recorder.

Notes

There is a better way to record calls on your iPhone or any other Bluetooh enabled phone? Check out my review of the Call Mynah.

  • It’s very likely that this is not the best (in fact it’s not), or the only way to accomplish recording phone calls on the iPhone, but it does work and it works well. I agree that the best solution would be a native iPhone app. but it’s my understanding that it’s not even possible to write an app. that records phone calls on the iPhone without using third party services like Recorder 10 and SpoofApp do (which they charge you for and are limited in functionality).
  • As Gizmodo “journalist” Joanna Stern pointed out this is a “fucking ugly” solution. What she fails to note though it that it works and is in several ways it’s better than any of the software solutions available.
  • While “Fucking Ugly” this solution does not require you to jailbreak your phone, you don’t have to pay per-min fees to use it, you can record both incoming and outgoing calls with it, your recording stays with you and is not on some third party server, it gives no indication that the call is being recorded, it lets you start recording mid-call, and it affords you the ability to use an external set of headphones and an external microphone even if you don’t want to record the call. In any case it’s certainly better than just rolling over and paying for an app. that does not do what you want/need it to do as “journalist” Joanna Stern suggests we all do.
  • Despite “journalist” Joanna Stern’s assertion this is not a “switch box” it does not use any switches at all.
  • I agree with everyone that it’s rather large but I used a project box that I had lying around; it could certainly be made to fit in a smaller box.
  • Several people have asked “If you willing to go through the trouble make this breakout box, why not just jailbreak? It woudl be easier.” First, I have not jailbroken an iPhone, but based on my understanding of the process, I’d say that for me the amount of work between jailbreaking and making this breakout box is about equal. For someone less familiar with electronics this may in fact be more work than simply jailbreaking but you only have to make this breakout box once, by jailbreaking your iPhone your entering a never ending arms race with Apple (at least if yo want the latest iPhone OS). Also, the only app. that is available for a jailbroken phone that records calls is SpoofApp. SpoofApp seems like a great app. but as mentioned in the beginning of this post it not only requires a jailbroken phone, you have to pay per-min fees to record calls, only works on outgoing calls, and your recording ends up on a third party server that you have no control over; a privacy issue.
  • You still get a little “talk back” but it is so mild that unless you were really, really, really listening for it you would not notice; it’s extremely mild. You actually have to blow in the receiver hard to get it to produce the effect.
  • The headphones act as a microphone with this setup but it’s so weak that it has no effect on the recording.
  • The headphone volume on the iPhone affects the level of the recording output.
  • Obviously (or maybe not) this setup requires that you to use a separate headphone and mic during calls – you could just use something like this.
  • The iPhone puts out ~3 volts on the mic line because it’s expecting an electret microphone. You could filter this with a capacitor but it probably won’t hurt anything. I’m assuming that I’ll always be using and electret mic so I didn’t add one.
  • The TRRS cable I used was actually just a 3.5mm video cable. This type of cable comes with a lot of video and digital cameras. TRRS jacks and cables are surprisingly hard to find – Mouser does have a TRRS plug but I could not find TRRS jacks anywhere.

Build Pictures

UPDATE: There is a better way to record calls on your iPhone or any other Bluetooh enabled phone – Check out my review of the Call Mynah.

Record iPhone Calls | iPhone Call Recorder

Record iPhone Calls | iPhone Call Recorder

Record iPhone Calls | iPhone Call Recorder

Record iPhone Calls | iPhone Call Recorder

Record iPhone Calls | iPhone Call Recorder

Record iPhone Calls | iPhone Call Recorder

Record iPhone Calls | iPhone Call Recorder

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