Mate there's no "special button". It's just the normal PLB "test" button. The same button tests the unit as normal (ie you get the green light if successful), it's just that the 406link bods are watching the skies and know that youve just pinged a satellite.
406link will work with many PLB's. There's a list here: Beacon List. Get one on this list and it should work with the 406link service.
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