The model I used was GE ESL350CX.
HERE is the thread where the information was originally posted.
Ya, I actually posted in that thread.

There was another thread
here that also went into detail about those smokes.
My plan was actually to get all 350CC's, and then 1 350CX. The CC's would all trip only if they detected smoke themselves, NOT by tandem. But the CX would always trip. So, that way I would ALWAYS get 2 indications when a smoke alarm went off, and I would always know that it was the CC fire alarm that caused it, thus showing me where it was. And, if I only got 1 indication, it could only be the CX, and then again I'd know which smoke was alarming.
I had a discussion with the wife, and I explained the merits of photoelectric vs. ionization, and so we may not end up saving the money after all. :lol: No better play to spend a little extra, I suppose. I'll ask the builder what they were intending to install (they aren't your average cheapo builder), but if it were ionization, I may just splurge on the smokes after all.
I had thought to put a smoke detector up in the attic as well....but that does bring up the question the builder posed...is there any known issue with smoke detectors in freezing spaces? The attic being unheated, it could certainly get cold enough up there. Same issue for the garage, which I thought was an obvious place for a smoke detector.