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When your computer stops functioning as expected, why do you assume you've only lost the AI transmitter signal? Let's say I agree that being unable to check your gas level is NBD...why are you so sure your computer isn't suffering some other failure that's also affecting the AI?
AI is an expensive, bulky, less than reliable solution in search of a problem. It's not going to kill you and data junkies should love the fact it means they don't have to do any thinking in order to determine gas consumption, but it's not much different from being a dangling Christmas tree of junk.
You're also saying two things about about the nature of HP hose failures: first that they quickly drain your gas (false), then that they take forever to drain a tank due to the pinhole restriction in the 1st stage's HP port (true). It's confusing, at best. But since you claim not be engaing in conjecture (hint to other readers: you are), let's hear your evidence for how an HP hose is more likely to fail than an o-ring.
Which is not to say that you're wrong about the transmitter vs. hose/gauge reliability debate. The transmitter has a single static o-ring (I'm assuming it's impossible for the pressure sensor to blow out...it's not, but it's so unlikely as to be irrelevant)...that's it. The SPG has that same o-ring plus a pair of tiny dynamic o-rings on an air spool plus perhaps another one in the hose. Technically, that's a few more failure points. Realistically, you're fairly likely to get some champagne bubbles at your SPG swivel connection sooner or later.
But the debate is pretty much moot because neither one suffers catastrophic failures ever. Seriously...aside from the early miflex hoses, the SPGs and hoses almost never break, burst, get cut, or extrude an o-ring. They bubble a bit, and you can still use them. AI, on the other hand, is either working or not working...and while the not working state is usually an easy fix, it still means you're aborting the dive. Not good.
We'll overlook that HP hose failures are a lot less common than transmitter link interruptions. You're clearly cool with ending your dives at the drop of a hat (or you're saying what you think everyone should hear you say, and would actually keep diving without the AI link...which is probably the most common approach).
JohnN, I’m also curious why you would want to dive with both a transmitter and an SPG? I don’t see any real benefits, just - well, extra clutter? If you’re worried about catastrophic air-loss, you’re only increasing the likelihood of that, by introducing more failure points. By adding a SPG to a transmitter, you’re getting rid of some of the benefits that transmitters actually convey (less clutter, more streamlining, less entanglement points (depending a lot on how you orient the transmitter on the first stage, but that another discussion.) If you don’t trust the transmitter - why dive with it? =)
I can imagine people that only dive on vacations might find this gizmo useful, but I can't imagine anybody that dives regularly requiring it.