Targa Miata
Click to see the next entry
June 20, 2009 - About 9 months late, we finally have some transit headsets for the car.
They were right near the top of our "things we need for next time list" last September. I think those long days in the car would have been a bit shorter if we'd been able to chat on the transits instead of simply putting in earplugs.
Part of the problem was our super Peltor intercom. Fantastic piece of kit, but the pieces are ridiculously expensive. Around $230 each for transit headsets. In fact, it would be cheaper to buy a separate Terratrip intercom and headsets than it would to buy a pair of Peltor-compatible heatsets from rallylights.com.
But I managed to find the part number of the headsets, and discovered that they're also used in the military. Sure, they have a 30 foot non-coiled cord and some weird military plug on the end, but you can buy new surplus ones for $200 a pair shipped. Some hunting around also unearthed the Nexus plug used by Peltor, and Aircraft Spruce provided a pair of those.
So, all I needed to do was figure out the wiring for the plug. Peltor was not interested in helping at all so I was on my own. The microphones on the helmets actually have a small connector on them, so it was a fairly easy job to use that to figure out that the two pins on the end of the Nexus connector were for the microphone and the next two were for the speakers. Chop the cable down, do a bit of careful wirestripping and soldering and voila! They work!
After a test drive, Janel announced that we really really really should have had these on the race. They work beautifully.
Now, for anyone who wants to duplicate the job, here's the parts list.
Peltor MT7H79A headsets (sourced from eBay)
Nexus TP-120 plugs (part 11-00699 from Aircraft Spruce

pin 1 (tip): black
pin 2: yellow
pin 3: red
pin 4: white

Pins 1 and 2 can be interchanged, there's no polarity that matters. Same with 3 and 4.

So there you go. That's how you make a set of Peltor transit headsets for half the price of new ones.
tags: intercom