Build a Ski Helmet Walkie-talkie ("ACS")




If you've been in a ski/snowboard shop lately you might have seen the K2 "ACS" system for their helmets, which integrates a headphone on one ear for stereo listening, and a headphone on the other ear with a boom mic for talking to your buddies over your walkie-talkies. You press on your earflap to talk and release to listen.

This looked like great fun and better than the usual hollering across the slopes and digging out our walkie-talkies when we lost each other. It also looked like too much money for 2 earflaps and a headset, when I had the materials at home to build it in half an hour.

Here, I make a busted Xbox headset and my ordinary K2 helmet into a K2 ACS helmet!

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Step 1: Modify Headset to Fit Under Your Earflap

With the broken Xbox headset, this was easy as it was already broken off of the part that holds it on your head. I just cut off the broken part and filed it smooth.

Remember, you want this to be comfortable. You are wearing it all day to ride!

Step 2: Reverse Earpiece and Microphone Connections, Add Talk Switch Connection

Most walkie-talkies use the opposite "polarity" on their connector to other headsets. So converting any phone/xbox/cell headset to walkie-talkies, usually requires popping it open and swapping the mic and headset wires.

Test it first! You may not have to swap the wires if you have weird walkie-talkies or a funky headset.

Use an ohmmeter to find the mic, earphone, and common wires. Leave the common wire alone.

Pics show before and after. Note the white and red wires have been swapped.

The simple swap is enough for voice-activated use, but on the mountain, the wind noise is too strong, and you need to use push-to-talk.

The pic I forgot to show... was of me adding the wires for the push-to-talk switch.

You want to put a hole in the headset (there's already one there on the xbox headset) and feed in 2 wires for the switch. Remember to tie a knot for strain relief, or they could rip right out and destroy all your work.

Now, don't connect the microphone to the pad where you were going to swap it to. Instead, connect it to one of the wires going out of the headset. Connect the other wire to the pad. You have put the switch wires in series with the microphone.

Step 3: Two-cent Poor Man's Switch.

I know I'll get booos for this one. But I used the 2-penny switch for a reason, and not just because it only costs 2 cents.

It's hard to find a switch as thin and with as little action as the 2-penny switch, which is perfect to slip between the headset and the earflap. It has a very large area which responds to a very small force, meaning you can slap at your earflap with your glove and it will come on. It also means there are no external parts to get snow in or look ugly.

If you find a thin switch that you can activate with gloves on then by all means, use that instead. Or mount another switch on the outside if you find a nice looking one.

Anyways, image 1 shows preheating the penny. It's damn hard to solder to a penny, so use a big iron and try to balance the penny somewhere it won't conduct all the heat away. Once solder starts to stick to the penny, you can solder the wire to it. Do this twice, once for each side.

Now it should look like image 2. Let it cool, and then build a thin spacer on half of one of the pennies with tape. Can you see the tape in the pic? Build it thick enough that it will not touch unless you were to press on it.

Then wrap the whole thing up in tape like image 3. Note the gap between the pennies. Test it well with your walkie-talkie. Most important - it must not get stuck on! It should require a light press, but not too light.

Step 4: Putting It All Together

Cut a small hole in your earflap and push the microphone through so it will go in front of your face. It should be a very tight fit.

Position the switch with tape or something and give it some tests with your walkie-talkie. It should switch to transmit easily and reliably when pushing your earflap with a glove on, but not come on when you tilt your head. You may have to adjust your penny switch spacer, too.

When you find a good spot, fix it there with your favorite adhesive. Don't use one too strong, in case you find that nice switch you were thinking of to replace the pennies.

Step 5: Push to Talk. Act Like a Jerk From Farther Away Than Usual!

"Do you require assistance?"

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    40 Discussions


    8 years ago on Introduction

    I know it's been a while since there was a comment, but I have a few questions. My friends and I play airsoft. I thought'd it'd be pretty neat if we bump-up the realism in the game with helmet (in my case a mask) to helmet communication. Now for the questions:

    1. I may not be getting this, but how do you sync up the walkie talkie and the Xbox Live headset? I skimmed over your instructions, but have yet to try it.

    2. Is it possible to have helmet-to-helmet communication? As in 1 Xbox headset to another Xbox headset, not to a radio. I would really only want just two headsets (for now, at least). I'm not really expecting this part to be possible with this current set-up, but any information you can give will be extremely helpful.

    I'm currently majoring in Electronic Engineering Technology, so I have a slight idea of what I'm doing. I thought that this would not only be quite helpful and efficient, but also great practice for the field I'm going into.

    Thank you for your time,


    8 years ago on Introduction

    might have to try this, i work as a ski patroller and its always hard to hear my radio


    12 years ago on Introduction

    Anybody have a link or schematic for the actual K2 headset ("Baseline ACS")? Trying to make it work with a yaesu vx-170 (2m radio) and its being a bear. Thanks, Joe

    7 replies

    Reply 12 years ago on Introduction

    the most common problem with these things is which part of the plug is headphone/mic. The ACS will be set up as a "FRS walkie talkie headset" - try a cheap cell phone headset or xbox headset, and see if the transmitter comes on. They are wired up the opposite way. The only thing on the schematic would be a switch between the mic and the plug to do the push to talk. Ring them out with the output from a stereo, tapping it to different parts of the plug - you won't hurt the mic, and it's disconnected by the switch anyways. Then find out which is which on the radio, and either make an inline adapter or modify one or the other. Never seen the vx-170, but there is always a chance it may use a different ptt system than the normal one (which turns on the transmitter when the mic is connected).


    Reply 12 years ago on Introduction

    Thanks. I played with it some this weekend and think I've got a handle on it. I had made some wrong assumptions that was making it a lot harder than it really was. If I get the right adapter coming out of the Yasue I think its going to just be plug and play. (And will still be able to use the MP3!) Another good example of why you shouldn't let a mechanical guy get too close to a soldering iron. Joe


    Reply 8 years ago on Introduction

    Tell me more about success with the Yaesu VX 170. I have the same radio and the ACS and the headset/mic 4 wire plug for the radio but need the schematic for the headset end.


    Reply 11 years ago on Introduction

    Alright, I just bought two K2 ACS' and a set of Cobra MicroTalk (PR-700 WXC) FRS/GRMS twoway radios that come with ear phones and mics. The walkie talkies have a button on the mic that came with them that you need to hold down for it to transmit. However when I plug my helmet in I can recieve a message but no matter what combination of buttons on my helmet and holding the talk button, I can not transmit. From reading your comment hear, I'm assuming the two conductors on the plugs are inverted. Do you agree? If so, can I just buy a cross over plug (I don't really want to go with the home made version). I don't have another headset available. Any suggestions would be greatly appreciated. Heading up the mounting on Friday. Thanks!


    Reply 11 years ago on Introduction

    I got the same problem with my ACS...just wondering if you ever got them to work with your radios


    Reply 11 years ago on Introduction

    Yes I did get it to work, all I had to do was not plug the helmet jack into the walkie all the way, I left it out about 2mm (put in a couple washers) and it works fine. Random eh?


    Reply 11 years ago on Introduction

    Yeah, but I had to go into the earphone and disable the PTT (push to talk) switch by shorting across one of the traces in the PCB (then glued the earphone back together). Did finally work though (using a wrist-mount PTT).


    10 years ago on Introduction

    Here's a "random" thought I was thinking about. What if instead of going around getting pennies and sawdering them to some wires, couldn't you possibly get some switches, like a on/off switch and make it so you can make it work the same? (and just in case someone else said this and I missed it sorry, but it is a little late for me)

    2 replies

    Reply 10 years ago on Introduction

    As mentioned in the instructable, most switches don't hold up in the environment of extreme cold and moisture. I have tried to swap in several push-button switches over the years since I wrote this and all failed (cracked plastic, dead spring, corroded contacts) - the 2-penny switch still works, so I guess it was a good call! A proper industrial button (think emergency stop button) would work great but would look stupid on the helmet. This one is invisible inside the earpiece.


    Or even a button... those wired buttin things you see on some older models of Vaccum cleaners... just in case u needed a visual

    That site shows the price of $55. Not too expensive indeed. But it would be more fun to MAKE your own! I've experimented with one that I made and it works with one bug. It REALLY picks up bass in your voice! Nothing that can't be equalized out.


    11 years ago on Step 1

    where do we get the power supply for the ski helmet???? will u please tell me which wire is swapped wtih the 2 penny???? does it require 2 helmets to be albe to communicate???? if it yes it means i should make 2 ski helmets????