To me, an octo is a traditional style backup regulator on a 36 inch yellow hose somewhere in the triangle . . . the secondary/backup regulator is attached permanently to a bungee around the neck and the primary regulator is passed to the OOG diver.
And, I fully understand what you are saying. And, it is your set-up, so do whatever works for you. My only comment was that the distinction you make is now an uncommon one, and not altogether accurate in current practice.
the designation is simple, in an octo set up the octo is passed to the OOG diver while in a backup/secondary model the primary is passed to the out of gas diver and the primary is traditionally on a longer hose (coming from a GUE standpoint)
In fact,
both an 'octo' - as you describe it -
and an alternate second stage on a bungee necklace, represent a 'secondary' second stage. There is no distinction. What is in your mouth for the majority of the dive is a 'primary'. Any other second stage is a 'secondary' (or alternate - or, if you insist on DIR terminology, a 'back-up') second stage. If it isn't the primary, by definition it is a secondary. Now, the valid distinction that can be made is whether you donate the 'primary' or donate the 'secondary' in an OOA situation, and that is a matter of procedure, not terminology. In fact, more than a few OW students are now taught to breathe from the second stage on the (longer, 36") yellow hose (possibly with a yellow purge cover in addition) as their 'primary', and to donate that primary to another diver in the event of an OOA situation, after which they go to their secondary (often on a bungee necklace).
lorenzoid:
The term "octopus," which refers to the backup/alternate second stage regulator and its hose, never made any sense to me.
LOL, I can understand. Here is an excerpt from
The New Science of Skin and Scuba Diving, for many years the 'bible' of scuba instruction (and, possibly, still the bible for some), that may have helped create such nomenclature: 'Easier than sharing a single regulator and mouthpiece between buddies is the use of an additional second stage attached directly to the air tank. Called an "octopus" because its use gives the scuba the appearance of having many arms, it has a longer hose for easier use by the needer.'
diver 85:
"a safe second"----when/where did that get started???....
As for 'safe second', I don't know the origin, but it has been around for a while (
http://www.scubaboard.com/community/threads/safe-second-v-octopus.21720/). I confess that I am personally not a fan of alternate inflator regulators (nee 'safe second'), but one thing that their use does is promote donation of the primary second stage in an OOA situation, and I AM a fan of primary donation.