How Smart Watches Work

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Introduction to How Smart Watches Work

2008 HowStuffWorks
The Fossil Abacus Smart Watch. See more timepiece gadget pictures.

There's no doubt that with the popularity of devices like BlackBerry, Palm Pilot and Treo, the trend in technology is to get more and more "connectivity" into smaller and smaller packages. The next step in this technological evolution is the Smart Watch.

Smart Watches give people access to news, weather, sports, stocks, horoscopes, MSN Instant Messenger, Microsoft Outlook and much, much more -- all from a wristwatch. In this article, we'll look at the technology behind the Smart Watch.

Smart Watches work using a technology Microsoft developed called Smart Personal Object Technology, or SPOT. Microsoft introduced SPOT at Comdex in 2002. Chris Schneider, Senior Program Manager of SPOT, describes the technology:

SPOT is a new computing platform designed to bring the power of .NET to everyday objects. SPOT allows for enhanced miniaturization, low power consumption and a low cost solution allowing for accessories such as watches to become more purposeful through the power of software.

Other Smart Gadgets

At CES 2003, Microsoft announced that the Smart Watch would be the first wide-scale application of SPOT. The technology could potentially be integrated into all kinds of everyday objects, turning things like key chains and refrigerator magnets into sources of useful data. For instance, a portable oven timer might be SPOT-enabled and connected to a service that provides hundreds of recipes.

Let's look at how SPOT works in the next section.

How SPOT Works

SPOT uses FM broadcasting, like the kind picked up by a radio, to deliver Web-based data to Smart objects. Smart Watches receive more than 200 channels of information that are broadcast on a radio spectrum leased by Microsoft.

Microsoft created the Microsoft DirectBand Network to send data to Smart Watches and other SPOT objects. DirectBand consists of two components: a special chipset in the watch that houses the radio receiver and a nationwide, wide-area network (WAN). The WAN is built on FM-subcarrier technology.

Subcarrier frequencies are usually above the normal frequency range used for audio and are modulated to carry data. For instance, in analog TV transmissions, a subcarrier frequency is used to carry information about color and other broadcast information. DirectBand transmits Web-based data on subcarrier frequencies using radio protocols designed specially for Smart Watches.

The DirectBand broadcast range covers 100 metropolitan areas in the United States and five major cities in Canada. In order to get this wide coverage, Microsoft partnered with ClearChannel and Infinity Broadcasting. This partnership allows DirectBand to broadcast data over a large, existing FM radio infrastructure rather than having to create its own.

Photo courtesy The SPOT Group
The SPOT Coverage area extends to 100 metro areas around the United States and five major cities in Canada.

To add DirectBand to an existing station, technicians install a piece of hardware called a broadcast generator. The broadcast generator injects the data stream directly into the FM broadcast that is transmitted to Smart Watches. The data originates from the DirectBand Data Center in Tukwila, WA. The streams are encrypted and transmitted from MSN through private frame relays, satellites and WAN networks.

MSN Direct is the Web-based component of the Smart Watch system that acts as a user interface for subscribers. The Web site can be used to purchase, activate and administer Smart Watches.

Photo courtesy MSN Direct
The MSN Direct Web site acts as a user interface for the Smart Watch.

To start a Smart Watch, a user must create a profile using a free .NET account. The activation process and setup includes entering billing information, location and the particular type of Smart Watch the user owns. Once the account is set up, the user can add, delete and modify the channels that are sent to the Smart Watch.

Photo courtesy MSN Direct
A user can add and delete channels on this page.

The channel system is based on "blocks." For instance, the test watch we used for this article had 1,000 blocks available on it. We chose from a list of channels, each of which had a block value ranging anywhere from 20 to 480 blocks. We were able to add channels up to our allotted 1,000 blocks. When we deleted a channel, its corresponding number of blocks became available.

In the next section, we'll see what's inside a Smart Watch.

Inside a Smart Watch

Photo courtesy The SPOT Group
The chipset fits on a PCB about the size of a U.S. quarter.

Currently, there are four companies producing SPOT-enabled watches. Suunto, Fossil, Tissot and Swatch all make Smart Watches of various sizes and styles. The designs vary from manufacturer to manufacturer, but in essence they all contain the same basic components.

Microsoft worked with National Semiconductor to develop the chipset used in Smart Watches. The chipset consists of an application chip and the tiny DirectBand custom radio receiver chip.

The watch we looked at is the Fossil Abacus. The Fossil Abacus Smart Watch has a rechargeable battery that is charged using a wall charger/watch stand. The photo below shows what we found when we opened up the watch.

Piezo (piezoelectric ceramic crystal) - This material expands and contracts when electric current is applied. The Piezo crystal in the watch acts as a tiny speaker driver, allowing the Smart Watch to generate sound.
PCB (printed circuit board) - A PCB is usually a multi-layered board made of fiberglass. The surface and sublayers use tiny copper lines to direct electricity to various components on the PCB. Motherboards, SIMMs and credit-card memory are all examples of PCBs. The PCB in the Smart Watch houses the CPU, memory and radio chip.
CPU - The Smart Watch is basically a tiny computer with a very specific job, and the CPU is the brains of that computer. The Smart Watch uses an ARM 7 TDMI as its central processor.
Memory - Also like a computer, the Smart Watch needs memory to perform its functions. The Smart Watch uses 512 KB of ROM and 384 KB of RAM.
DirectBand radio receiver chip - This chip was made specifically for the Smart Watch and is how the MSN Direct service connects to the watch. These chips are the heart of SPOT technology.
Battery - The Smart Watch battery is rechargeable. The Fossil Abacus comes with a recharging stand, but other models use an adapter that plugs into the wall. The amount of time you get out of each charge varies greatly and depends on how much "channel surfing" you do (and on the model of Smart Watch you buy). The Abacus can function for up to two days on a single charge.
Inductive charging coil - This is used to charge the battery. The coil is attached to the contact surface on the back of the watch. When this surface comes in contact with the charging plate on the watch stand, the Smart Watch battery is charged through induction.

Abacus Smart Watch on its charging stand

It will certainly be interesting to see if SPOT technology becomes integrated into our everyday lives in the years to come. The SPOT team continues to work toward applying SPOT technology in a variety of objects as well as expanding its current functionality.

Bill Mitchell, founder and general manager of the Microsoft Smart Personal Objects Technology group, had this to say about the future of SPOT:

... it's important to remember that the goal of SPOT is not to create new devices but to take devices that have a proven usefulness and make them more functional. It's also important to remember that in the future, SPOT devices will not just be isolated displays of information. We foresee a time when SPOT devices, PCs and other computing devices will interact with each other seamlessly.

For more information on Smart Watches, SPOT technology and related topics, check out the links on the next page.

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