thanks caves4me, and YES, the Petrel / Petrel 2 are the "best in class."
yet, for my needs, the dual transmitters on the Hollis TX-1 seems very interesting. of course, I need to check/compare the tissue algorithms against my current dive computer, to see that my alerts, etc. continue in same margins. God forbid the Petrel thinks there is an expert on board !!!
what will be an advantage for my needs, because of my dependence on alarms, is that possibly the TX-1 can prompt me with NOISES, BELLS and WHISTLES blasting as I ascend, reminding me to switch gases.
you guessed it, I stand with my head is bowed to those to have the Petrel / Petrel 2 and can get adjusted to its expert technology super quickly. as for me, "holding hands" with my next dive computer is not a bad idea.