Mike,

> > I understand things from Draeger's literature and through speaking with
> > their representatives and Dolphin users, there are still a few negatives.
>
> There are negatives with EVERY rebreather out there.

Ok, give me the negatives that are life threatening on the Halcyon.

> > First, you are betting your life on your O2 analyzer, not just on just the
> > oxygen toxicity side, but also, as Carl pointed out, on the hypoxia side.
> > The more stress you are under or the more vigorously you move the lower
> the
> > PO2 and consequently the oxygen available to your brain.
>
> You are betting your life on your O2 analyzer for any gas dive, be it open
> or closed circuit.

What?!  If I do an OC gas dive the O2 analyzer is *NOT* used in a life
support manner.  I *mix* the gas and I already *KNOW* what percentage
the O2 is.  That O2 analyzer is only used to *confirm* what I already
know.

In some CCRs the O2 measuring system is used to determine how to mix the
gas FOR you or provides you with information that YOU must use to mix
the gas manually.  This is information that that you have NO WAY to
confirm independantly.  Systems like the Dolphin are only *SINGLE*
measurement systems.  From that perspective at least other units
(like the Cis Lunar) have a triple redundant measurement system.

Plus, if one of the O2 measurement cells "sticks" (which must be
detected
by the user!) there are methods of "clearing" that stick such as blowing
diluent across them (I believe this method is available on the CL).
No such "manual" method of clearing a stuck device exists on the
Dolphin.

> I have a bail out system that I use so drive bottle  size does not matter...

But you have to *realize* that there's a failure.  That realization is
NOT
guaranteed, however, I bet dollars to donuts you WOULD recognize a
continuous
shortening of breatheable air (which is how the Halcyon reacts to an
out of gas situation).

> Wrong. The Dolphin  has three orifices for gas.

3 orifices!  That's even better for the kinky people out there :^)

> Have not heard a noisy belch yet. Unit does release bubbles, but it is not
> particularly noisy, much less so than open circuit and a smaller amount of
> bubbles also.

It's not as noisy as OC but it is definitely still there, however, once
you become "complacent" you tend not to hear it anymore.  I found that
happening as soon as my 2nd dive on the thing.

> Don't know about your experience with it, but I find that I am able to get
> much closer to the fishies with the Dolphin vs Open circuit...

I don't doubt that you can get *closer* but it's still not optimum.
Now,
pretend you're at 66'.  With a Halcyon not ony would you have the
reduced
gas due to recirculation but that volume would be further cut down by
a factor of roughly 3 at that depth.

> Ditto with every other breather out there...

Yep, most serious rebreather divers take along bottles of O2 and He with
them, or, have them shipped ahead of time.  This isn't a "cheap" way of
diving.

> >         Of course, because of the counter lung, it is much more difficult
> to
> > control one's depth and consequently to approach fish smoothly and
> > naturally.
>
> Excuse me? I found that after 4 or 5 dives on the unit, buoyancy control was
> a non issue.

I agree entirely here.  The RB only amplifies bad bouyancy.

> > Moreover,
> > because of the insidious nature of hypoxia and the structure of Draeger's
> > technology, I believe Carl's insistence on an Oxygauge is well founded.
>
> I agree that it's well founded also. I don't agree that it's a toy or should
> only be dived in ones bathtub.

Ok, I'll add the shower in too and the shallow end of the pool.

Carl