The next iPhone will be released some time this fall and speculation has come down to two basic time frames, some time in September or some time in October. One indication that the iPhone 5 may arrive sooner, rather than later, is the fact that the hardware has been delivered to carriers for testing, according to The Guardian’s Charles Arthur.

Arthur says that the boxes used for testing have been delivered to the carriers to ensure compatiblity. These boxes are designed to enclose the hardware so that the phone is impossible to photograph or even be seen by technicians. The technicians are able to connect to the devices for diagnostics, but are mostly unable to open them or see the devices. A select few employees that are allowed to see inside the boxes, but even then all they see is a dummy body.

This procedure is very similar to the way that the iPhone is tested in areas of Apple outside of the design department. This way, even engineers are not privy to the way that the phone will look and instead connect to a device hidden inside a box.

Now that the phones are at the carriers for testing, they will undergo a certification process and be approved, which normally takes just a few weeks. Once that is done, Apple can move ahead with manufacturing. It’s important to note that any testing here is going to be related to modem software used to communicate with a carrier’s network, and not hardware, which has likely been finalized for some time now.

The issue with getting too excited here is that, yes, those are sealed boxes with some mystery equipment inside, but they could easily be something else. Since very few people are allowed to see what the product is, there is no way that the sources quoted are 100% sure that the next iPhone is in there. That being said, if you’re seeing mysterious black boxes being delivered to your carrier’s labs from Apple, just weeks away from a possible release date, well, it’s not hard to connect the dots.

Every bit of information that we here at TNW have seen or been told personally is pointing us to a September announcement for the iPhone. Whether that means that the phones begin shipping that month, we haven’t heard. If Arthur’s sources are accurate, and the phones have been delivered to the carriers for testing, then it is likely that a September shipping date is in the cards. This also makes sense from a quarterly profit perspective, as sales from September would go on Apple’s Q4 books, spiking the numbers for the pre-holiday quarter.

We’re not in the business of making release statements on behalf of Apple, because the company has been known to change release dates and announcements right up to the moment, but it is looking likely that September is the month to block off for an iPhone 5 announcement at the very least.