Saturday 18 January 2014

Hacking the Bose Triport Tactical to work with your smartphone (or walkie-talkie)

The Bose Triport Tactical Hedset is actually a rugged noise cancelling pair of headphones and I therefore HAD to play with them.

My conclusions were however that these are useful if you want to hear both ambient noise and your radio (you can read my review here) simply because soldiers are meant to hear each other. This is its major difference with its little brother, the Bose Quiet Comfort 15 (QC15). The one I got was unfortunately broken: the speaker of the right ear cup was defective and although this part is not serviceable, it can still be swapped with a spare one (write-up in my other article here).

This short article will describe the journey to make it work with a smartphone or walkie-talkie.

No manual: how it works and investigating the pinout

How to use it

The headset came with no manual or whatsoever. Here are my observations about how to use it:
  • The headset uses a AA battery but works with no battery in it. 
  • When switched off, it offers a good passive noise insulation
  • When switched on, ambient noise is repeated inside the headset. The volume is however adapted to remain within a safe range.
  • If you decide to use a battery it will last many many hours.
  • The PTT button can be pushed to talk (downwards) or latched (upwards)
  • It is heavy but feels light on the head (it is well balanced)
  • When connected to a compatible radio, Active Noise Reduction is active. It is however possible make it work unconnected.


The specs of the AP-107 connector (or more precisely the AP-107BR, specs here) do not provide the pinout. With a little trial and error I came to the following conclusions (see picture below):
  1. VCC for the Active Noise reduction (yellow, anything between 5.5V and 32V DC)
  2. GND (black)
  3. Left ear (blue)
  4. Right ear (white)
    Note: both left and right channels are connected to the same pin of the connector, see below.
  5. PTT (orange)
    Note: the circuit between the orange and GND wires are closed when the PTT button is pressed down (momentary) or up (latching).
  6. Mic (red)
  7. GND (green)
  8. Not connected
Results of my pinout investigations
This is the pinout of the cable going from the radio to the battery compartment. The numbers correspond to the pin numbers inside the battery compartment (from left to right, holding the battery compartment with the cable to the headset up). The picture of my notes on the above shows how these wires are wired in the connector (front view, with the contacts facing you as on the first picture above).

From mono to stereo headset

This headset is stereo but has both channels connected to the same pin in the original radio connector. I am therefore going to get rid of that connector and place a new one. My objective is to connect it to a smartphone (and a Midland radio which has a different pinout).

For those interested, here is how I found out the headset had separate audio channels:
This headset is meant to be connected to a mono audio source and it is for this reason it has only one audio input on its connector (both the blue and white wires are connected to a single pin on the connector (see above). I had found this with some trial and error: both ears are connected to separate noise cancelling circuits each individually connected to the main box. Based on this observation I went a little deeper in the pinout analysis of the connector and noticed that the audio-in pin of the connector is actually connected to two pins in the control box... after removing the cable (used to connect the headset to the radio) and connecting an audio source to the GND and pin where the white wire came in I got sound in my right ear only Hurray ! I did the same with the pin for the blue wire and got sound in my left ear.
The battery compartment opened. I removed
the wire to the radio and the DC plug.
On the top right: the 4P 3.5 female jack socket
I'm going to use.

Preparing the headset for the hack

Open the battery compartment ; this is where we are going to work.

Remove the original wire intended to be connected to the radio (remove the silicone gluing it in place).

Below I will describe why I'm making extra room by removing the DC socket that is used to plug the headset in a combat vehicle. This room will be useful if you want to use standard cables and keep your headset versatile.

Making a pin header so the connector pinout can be easily rewired when changing devices

I want to use a simple 4P 3.5mm male/male cable to connect my headset to my old Samsung phone. I want the PTT button to be useable with the phone but I also want to be able to use it with my Midland walkie-talkies.

As you would have expected different devices come with different pinouts but usually have standard connectors (this is the reason why I used a 4P female 3.5 socket). While most smartphones use the following pinout: left, right, GND and mic (starting from the tip of the jack) Midland radios don't and I will therefore need an adapter.

Things get harder if you want to be able to use the PTT (push to talk) button with your phone and with the walkie talkie. Depending on the device you use, the button will behave differently (electrically speaking):
  • Smartphone headset: shortens the mic and ground pins
  • Midland: connects a 470R (ohm) resistor between the mic and ground pins
This is problematic since 470 Ohm between these pins will behave differently on a smartphone (previous track I think) and shorting the mic and GND will prevent the mic to work on a walkie talkie (or any other configuration, really...). This means you need to use a 6 pin connector on the headset to be able to wire all functions as you need them (left, right, mic, GND and 2 for PTT)... unless you decide to use a pin header to rewire them depending on the device you connect it to.

This is the reason I removed the DC socket that would normally be used to power the device in a combat vehicle (I don't have any) and added a pin header to make it easy to rewire the 3.5mm socket. The picture below shows the connections I made:

Wiring diagram for the 3.5mm 4p socket, the pin header and the
connector inside the battery compartment

Assembling it all nicely inside the battery compartment

The pictures below show the realisation of the diagram above. The 3.5mm 4P socket was recovered from a headset extension I purchased on eBay some time ago. The rest I just had lying around.

Note that the hack here involves lots of hot glue to secure all components in position. It also comes with the advantage to make things waterproof.
The 3.5 socket connected
to the pin header itself
wired to the connector going
in the battery compartment

My 'smartphone' male pin header
I made another one with a resistor
for my walkie-talkie

The battery compartment ready to
be closed (and used)

The completed hack 
Note: This page provides valuable information on walkie-talkie pinouts, including Midland's.

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