The cable is wired pin-1 to pin-1. That is to say, the two ends are 180 degrees flipped. But little good this will do you since you will have to chop it in two and adapt it to your project since the mating connector is not distributed in the USA. Not even by US Global, the mfg of the module.
The serial output is 0-2.8V. This level may be too low to *reliably* drive some 5V TTL devices. The serial input to a typical PIC will need a 3V-to-5V buffer if the PIC is powered by 5V. I learned the hard way on that.
From what I was told by USGlobal, the EM406's serial command Input (pin-3) is 5V tolerant. There is nothing about this in the manual (it states 0V-2.85V TLL). I have been using 5V TTL level RS232 and have not harmed the module, so fingers are crossed that the info is correct.
I am interested in hearing from other EM406 users. Although it has incredible sensitivity and can quickly obtain satellites locks (even indoors while covered by a metal pie plate!!), I am disappointed in its overall performance.
The data is very unreliable, especially when stationary. For example, while sitting still it will usually report that it is moving at 3-5 knots, course will bounce in every direction, and the like. And for some reason, traveling directly west sometimes gives inaccurate course data, but the other compass points are fine. This is with 10 satellites in view and a HDOP under 1. WAAS on or off does not change this either.
