The Alpine TUA-T550HD is an HD Radio tuner module, which, when connected to an Ai-Net compatible Alpine car audio receiver (nearly all of them are), allows the reception of digital radio broadcasts. The device is fairly straightforward: you connect it between your car's antenna and the receiver and the broadcasts come in.
However, when the TUA-T550HD is connected to one of three very specific Alpine receivers (iDA-X100, iVA-W550 or iDA-X100M) and a compatible Apple iPod, an additional function is activated: iTunes tagging.
Designed to be tucked out of view and controlled remotely by the Ai-Net compatible receiver, the TUA-T550HD is simply a metal box. At one end is the connection for the wire harness that supplies the TUA-T550HD with power and at the other are the input and output ports for Ai-Net connections, USB input and output ports, and an input for connecting the vehicle's existing AM/FM radio antenna.
The TUA-T550HD's simple design means that it can stand up to a fair amount of abuse from bumps and kicks, but you'll want to mount it out of the way, for example, under the seat or behind the dashboard.
Installation of the TUA-T550HD is as simple as finding a location for installation in the vehicle's cabin and bolting the unit to the vehicle's body. The included Ai-Net output cable is routed from the device to the receiver. Any other Ai-Net compatible devices--such as CD changers or satellite radio receivers--can be daisy chained through the TUA-T550HD's Ai-Net input. If using the TUA-T550HD with an iPod compatible receiver, the units are USB connected and the USB pigtail is routed to an accessible location, such as the glove compartment. Connect the vehicle's antenna to the TUA-T550HD using the included antenna extension cable. Finally, tap 12 volts power and ground locations and connect the wire harness.
When connected to a compatible iPod and one of the aforementioned iPod compatible Alpine receivers, the TUA-T550HD gains the ability to iTunes Tag song information. When playing back an HD Radio broadcast that includes artist and song title information in its text stream, simply hold down the select button on the receiver to save the metadata onto your iPod. Later, when you connect your iPod to your computer for syncing, a new playlist will appear in iTunes under the Store heading called "Tagged." In this playlist will be the songs tagged earlier with--if available in the iTunes Store--a 30-second clip. If you still like the song at this point, you'll be able to download the song from the iTunes Store.