I've had an external Bluetooth adapter on my Mac for a long time -- since the earliest days of its support in OS X. Back then, I used it to pair my Palm with my Mac for wireless synching. Since my previous Macs never had built-in Bluetooth, I purchased a USB Bluetooth adapter -- at the time, that was a Belkin F8T001. It worked fine for the last few years, until I added an Apple Wireless Keyboard to my system. In the Bluetooth System Preferences panel, there's an option called "Allow Bluetooth devices to wake this computer." On my Mac, it was perenially dimmed. This never bothered me much, as I just moved the (USB wireless) mouse around to wake the machine.

Then came the release of 10.4, with support for Bluetooth headsets. As I'm involved in a fair number of audio iChats, and already had a Bluetooth headset for my phone, I was really looking forward to this feature. Alas, after upgrading to 10.4, my Mac couldn't pair with my headset, so I just gave up for a while. Recently, though, I thought I'd look into the problem again. A quick search of Apple's Knowledge Base found the fix -- this article described the problem exactly, and provided the solution: It turns out that there are only two Bluetooth adapters that support this feature: Apple's built-in adapter, and the D-Link DBT-120, revision B2 or later.

So it looked like I just had to "throw some money" at this problem to solve it. It turns out that was almost, but not entirely, correct...

After a quick trip to my local Apple retailer, I had my DBT-120, revision B4. Note that if you buy one of these things, D-Link can't quite seem to decide how it wants its labels to look. Check here for pictures of the different versions, so you know what to look for in case of old stock at the store.

Excited to test out the new wake-from-sleep and headset features, I checked the nine-page DBT-120 installation guide, just to make sure I wouldn't miss any of the steps. I got a laugh from the fact that, of seven pages in the installation guide, exactly two sentences and one picture are devoted to the Mac installation--it basically says "Plug it in. Use it."

So after working through the tough install, I opened up the Bluetooth system prefs, and found ... nothing had changed! I still couldn't pair my headset, nor could I wake from sleep. At first, I thought this was because I had the adapter plugged into the monitor, not the Mac itself. But a quick swap didn't help.

After some digging with Google, I found the answer in a Macintouch reader report. An anonymous reader wrote that "even if you buy a new DLINK #DBT-120, you will still need to apply this firmware update to support the Bluetooth Headset Profile; it doesn't support it out of the box." Back to Apple's site I went, where I found the Bluetooth Firmware Updater 1.2. One download and install later, and all the issues were resolved -- pairing the headset works perfectly (though using it in iChat is a bit of a pain), and most usefully, my keyboard can finally be used to wake the Mac.

The version of the firmware installed by the updater is 2.1586. I didn't note my exact version number prior to running the updater, but I know it was in the 1.5x range. Part of what confused me is that I thought the "1.2" portion of the updater's name referred to the firmware version. It doesn't; it refers, of course, to the version number of the updater itself. The moral of the story is that, even if you have a brand-spanking-new DBT-120, it's quite possible its firmware is out of date. If things aren't working right, try the firmware updater...

Useful related tip: While digging for thsi solution, I found that Apple has a thorough Bluetooth support page that contains a fair amount of information and troubleshooting assistance.