iPhone ChatterBox Cable

I am presently on a quest to get my gear connected. My iPhone to pump music and phone calls into my helmet, and my ChatterBox HJC-FRS so that I can communicate with other riders and my passenger. I do listen to music on long rides to break up the wind noise, but don’t really plan on making phone calls while driving. (probably just listening in on early morning conference calls) So how am I going to do this? The obvious solution is to use the equipment I already have and modify it to meet the requirements. So here’s the inventory. EDIT: This cable may break your ChatterBox. I have discovered that the Microphone circuit on my ChatterBox no longer transmits! I do not know if it was this cable that did it…

The HJC-FRS has four inputs;

1. MIC-SP: for the helmet speakers, and microphone
2. Intercom: to connect the passenger’s helmet mic-sp headset
3. PTT: for the push-to-talk button ( I made one of these but that was a different project)
4. AUDIO: a 3.5mm jack for MP3 players etc.

Th iPhone has two input/outputs I’m going to try using the 3.5 mm 4 conductor jack on top. This provides stereo audio and microphone input, and well as the ability to pause, skip, hang up and answer if you short out two of the wires with a button…just like the hands free headsets.

The Plan:

Make a cable to connect the iPhone’s 4 pole jack to a 6 pin mini din jack on the ChatterBox.

The Diagrams:

This diagram shows the pin outs for the jack view, looking at the back of the ChatterBox. When soldering the wires this is the view of the pins as well.

This diagram shows the pin outs in the iPhone plug.

The Parts:

The easiest way to get the parts for the cable…Amazon.com.And a grand total for the parts $1.81 !!! The cable I spec is nice and round so it fits perfectly in the din plug. Here are the part numbers;

• $0.65 iPhone cable (camcorder vid-aud cable): link to cable on Amazon
• $1.16 6 pin mini din plug: link to plug on Amazon

The Assembly:

After the cables arrived I soldered them up using the pin outs circulating on the internet. If you buy these exact cables these colors should match up, but double check with a continuity tester to be sure.

Note: The cable I bought can be disassembled and desoldered, not cut. Use an exacto knife and carefully split the plastic triangle. Inside you will find a PC board and the wires are soldered to that. Now all you have to do is re-solder them to the pins. Nice.

Note: The din plug needs to be trimmed a bit. The outermost sleeve is 2mm too long. Because the HJC-FRS has a recessed jack trimming the outer sleeve down a bit will give it a step down so it fits better in the ChatterBox. I would lose the right audio on the ride because the plug was not seating all the way,m so trim it before assembly. Slide this onto the cable before soldering.

To bridge the grounds I cut a little off the left over RCA jacks pig tails and soldered it onto pin 1 and pushed the blue and bridge together and soldered them at the same time.

REMEMBER: The pin outs diagram is looking at the back of the din plug!

The last step is wrapping the back of the jack and wire with ~3 wraps of electrical tape. This protects the wires, and allows the plug to grip the wire and reduce the chance of the wires getting pulled out.

The Results:

How did it work? Ok. It works, but it isn’t perfect. The intercom input bypasses the volume control, so the iPhone volume is what controls the music, the volume knob on the ChatterBox does nothing to boost or attenuate the volume of the music. It will however cut the volume down by ~30% when the ChatterBox is turned on. In other words turning on the bike-to-bike radio will reduce the volume of the music, and it’s noticeable. Bummer.

Here are a few other options I have thought about;

1. iPhone earplug headphones with a wind guard on the mic stuffed into the helmet in conjunction with the ChatterBox, intercom still available, separate volume controls
2. Bluetooth headset disassembled and wired into the intercom jack, but then I can’t talk to my passenger
3. New ChatterBox with Bluetooth built in…expensive ~$400

Option one here may be the best/cheapest solution… Any other ideas?