by Jason Snell

AirPort Express is a product that manages in true Apple fashion to be about a half-dozen ideas rolled together into one small white plastic box.

Looking weirdly like an Apple power brick (it measures less than 4-by-3-by 1 inches, and weighs less than 7 ounces) , the US $129 AirPort Express is an AirPort Base Station, a wireless relay, a wireless bridge, a music streamer for stereos and powered speakers, a wireless print server, and an answer to the prayers of PowerBook-toting business travelers.
http://www.apple.com/airportexpress/

Let's start with the basics, the AirPort Express is an AirPort Base Station that fits in the palm of your hand. It doesn't offer all the niceties of the UFO-shaped AirPort models, such as support for up to 50 users, separate LAN and WAN ports, an external antenna connector, or a built-in modem. This means that Apple has finally released an AirPort Extreme base station that's more reasonably priced for casual home users.

But I suspect AirPort Express will really shine as an additional wireless product. For example, you can use it as a relay point in concert with an AirPort Extreme Base Station to extend the range of your wireless network and help you bring Internet connectivity to dead spots in your home, office, or school.

For business travelers who've gotten used to working wirelessly, being tethered to a short (and often inconveniently placed) network cable in a hotel room can be infuriating. But I imagine a whole bunch of those road warriors will soon be including an AirPort Express in their travel kit; once you get to the hotel, we'll plug an AirPort Express into the wall and the broadband cable. From there on out, we'll be able to surf wirelessly from the desk, the bed, the couch, heck, even the bathroom sink!

AirPort Express also has a USB port and the same USB printer-sharing features as its AirPort Extreme cousins. So if you've got a shared printer in your family, office, or classroom, you can place it in a central location and attach it to an AirPort Express, making it available to everyone on your network.

If you're using AirPort Express as a base station, you'd plug your Internet connection into it via its included Ethernet port. But if your main base station is an AirPort Extreme or AirPort Express, you can also use the AirPort Express as a wireless bridge -- just plug it in somewhere else in your house, and attach any Ethernet-based device to it. That device will now be on your network, even though it's nowhere near the rest of your stuff.

But I haven't even mentioned the most radical part of the AirPort Express, the part that will probably sell more AirPort Expresses than any of the features I've mentioned up to now:

It's got an audio-out jack on it.

That's because AirPort Express is also an audio streamer, letting you connect any set of powered speakers or any stereo with a mini-jack- or optical-audio-input to your iTunes library and play music remotely. Stick one next to your home theater receiver, and you can listen to your iTunes music collection. Thanks to an update to iTunes (version 4.6), iTunes will now be able to play music either through your computer's speakers or through speakers attached to any AirPort Express -- you choose where the music goes via a pop-up menu at the bottom of your iTunes window.

It's encouraging to see Apple embracing digital music in places away from the Mac or the iPod. Of course, you must still use have iTunes open and running on a computer in order to play music to AirPort Express... but a lot of iTunes users want exactly what AirPort Express will give them: an easy way to play their tunes through their home stereo, or to a small set of speakers on the back porch, or into a child's bedroom.

How AirTunes Works

Essentially, AirTunes is a method of creating remote speakers for a copy of iTunes, and sending data to those remote speakers via a wireless network. That network can be formed by connecting an AirPort Express to another AirPort Express, to an AirPort Extreme Base Station, or even to a non-apple 802.11b or 802.11g access point.

When you select an AirPort Express device in the new pop-up menu at the bottom of the iTunes 4.6 interface, that device essentially replaces your Mac's speakers as the audio-output source for whatever you do in iTunes. At that point you can do anything you'd normally do in iTunes -- play music from your Library, from someone else's library, or from your iPod; play an Internet radio stream; even play an audiobook. The sound won't come out of your Mac -- it'll come out of the speakers attached to the AirPort Express.

For those wondering if AirPort Express supports MP3, AAC, or any other specific file formats, the answer is no. AirPort Express supports Apple's Lossless Compression technology -- and everything that your iTunes streams across the network to Airport Express is compressed using that technology.

iTunes does the heavy lifting. When iTunes plays back standard audio content (AAC, MP3, audiobooks, music streams), it decompresses those file formats and creates what's essentially a raw, uncompressed audio stream. That stream is compressed on the fly using Apple's Lossless Compression, encrypted, and sent to the AirPort Express. AirPort Express decrypts the stream, decodes it, and outputs it in either analog format (if you plug in a standard analog mini jack) or as a digital PCM stream (if you plug in a mini-sized optical cable, which you can get from most major cable suppliers or straight from Apple for US $39).

If iTunes is playing back a digital multichannel file format like AC3 (Dolby Digital) or DTS, those bitstreams are wrapped in Apple's compression and encryption, and then decoded at the other end. In those cases, AirPort Express would end up streaming the raw AC3 or DTS stream via an optical cable to your home theater receiver for decoding.

This means that if you're currently listening to music on speakers attached to your Mac, AirPort Express doesn't change the Mac side of the experience at all: you're still using iTunes as your musical interface, and you've got to keep that Mac on and iTunes open in order to keep the music playing. (As opposed to a device like Slim Devices' Squeezebox, [http://www.slimdevices.com/], which is operated by an infrared remote control and has its own display to show you what's playing and let you change what you're listening to.) You can also only play one thing at a time, and to only one set of speakers. But now those speakers can be just about anywhere.

http://www.macworld.com/weblogs/editors/archives/2004_06.php