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Flash Memory Distribution of Digital Talking Books

February 2005

by Neil Bernstein, Information Technology Specialist

In 2008 the National Library Service for the Blind and Physically Handicapped (NLS) will begin to replace its existing cassette-based talking book system with a new system based on digital talking books (DTBs). These books, recorded and played back using digital audio technology, will provide the same top-quality narration NLS patrons have come to expect.

Along with digital audio must come a new medium to replace the analog cassette. This new medium must be as easy to use, as durable, and as simple to duplicate as the cassette. Ideally it would also hold far more audio, be reusable, and still be of reasonable cost. For these reasons NLS has chosen the USB (Universal Serial Bus) Flash Drive for the circulation of DTBs

This choice was made after considering alternative digital media carriers such as CD-ROM and the miniature hard drive.


The CD-ROM is an excellent carrier of all kinds of digital information, including DTBs. It is inexpensive and easily duplicated. However, braille labeling of a CD is extremely difficult, and the machines required to play them include fragile electro-mechanical parts. The loading process either exposes some of the most fragile parts or uses a slot-loading mechanism that would be far too prone to breakdown. These machines are not easily repaired and, because of their moving parts, have greater battery requirements than solid-state systems based on flash memory.

Perhaps the biggest strike against CD-ROM, though, is that it does not lend itself to repeated circulation. CD-ROM discs are very easily rendered unusable by handling, especially by people with limited dexterity. One-way library systems based on CD-ROM, in which the discs are not returned by patrons, have proven cost-effective elsewhere in the world, but such a system could not be used in the NLS program. Every patron request would require on-demand duplication. The technology to support this (which would entail massive local storage or high-volume data transmission as well as local labeling and packaging) is sufficiently complex and expensive that duplication could not be handled at most network libraries. Centralizing all duplication and circulation in NLS-funded centers would not be feasible, as it would transfer to NLS the full cost of circulation—something the NLS budget could not support.

Magnetic hard drive:

The prices of small hard drives have dropped considerably in the last few years. These devices could hold up to three hundred DTBs each when fully loaded. However, a system based on these devices would suffer from many of the same difficulties as a CD-based system, including shorter battery life and difficult-to-repair parts. While receiving three hundred books at a time might seem a blessing, most patrons would ultimately find this overwhelming or inflexible, as the drives could be reloaded only infrequently (perhaps as seldom as every two years), thus limiting access to bestsellers and new releases. Further, navigating a selection of three hundred titles would be daunting for many readers.

USB Flash Drive:

It is the USB Flash Drive that, although not as cheap as the CD-ROM or as capacious as a hard drive, strikes the perfect balance of durability, capacity, and cost.

These credit-card-sized devices, which can hold an entire DTB, will be used with the forthcoming DTB player from NLS. The USB Flash Drive contains flash memory, a type of computer memory that can be read from, written to, or erased and that does not lose its data when power is removed. This is the same kind of memory digital cameras use to store pictures.

Why flash memory?

Flash memory has many advantages over other carriers of digital media such as tape or disk while retaining most of those formats' benefits.

No moving parts

The use of flash memory as a DTB medium means that book players have no moving parts and thus have far fewer parts to wear out, resulting in a longer-lived machine. Also, the players will generate far less heat than a tape- or disk-based player and can get equivalent battery life from a smaller battery. As a result, flash-based players are smaller, lighter, and faster to recharge.


Unlike CD-ROM, flash memory cartridges are sturdy and reusable. Their toughness, already legendary (see "Durability," below), is matched only by the ease with which their content can be changed: simply plug the cartridge into a computer-attached writer and transfer a book directly to it at high speed. (Of course, the cartridges circulated by NLS will be rewritable only by those responsible for their circulation.) Cartridges can be rewritten thousands of times, so NLS can take copies of a book in and out of circulation as needed, meeting patron demand without wasting materials. This reusability easily makes up for the difference in cost between flash memory and other media.

Titles can be mass- or individually duplicated

Though they sound specialized, flash memory cartridges can be mass-duplicated just like any other media. A bank of writers can copy a DTB to multiple cartridges simultaneously or, just as easily, write a different book to each cartridge. Books can also be duplicated as needed, one at a time, by libraries. This flexibility makes available any number of scenarios for the large- and small-scale duplication of titles.

Widely available, mature technology

Flash memory is by no means a new technology. It came into widespread use more than ten years ago and can now be found in nearly every electronic device, from microwave ovens to televisions and automobiles. It is the recent precipitous drop in prices, driven by the popularity of digital cameras and portable digital audio players, that has made the use of flash memory economical for NLS's purposes.

Continuing to get cheaper and cheaper

The price of flash memory is dropping rapidly, between 30 and 40 percent each year, according to Gartner, the nation's leading provider of research and analysis on the IT industry.1 If present trends continue, the price of cartridges to be used for NLS DTBs may soon be only a few dollars each, with the memory chip itself costing less than the other electronic components and the cartridge housing. Cost trends are discussed in more detail below.

Multiple sources

Flash memory's widespread use and high demand have spurred many manufacturers of integrated circuits to begin producing flash memory. Well-known names such as Intel, Samsung, and Toshiba are continuing to add to their manufacturing capacity, competing with flash-memory specialists like Lexar, SanDisk, and others, resulting in an abundance of inexpensive parts in the time frame targeted by NLS for its transition to digital systems.

Flash memory is clearly the right medium for the distribution of NLS's DTBs. An adaptable technology, it is available in many different formats. Of those, only one is ideal for use by NLS: the USB Flash Drive.

What is a USB Flash Drive?

A USB Flash Drive is a piece of rewritable, nonvolatile memory that can be inserted into and removed from an electronic device. Like the familiar computer floppy disk, files can be transferred to or from it. And like a floppy disk (and unlike the memory found in a computer), the data on a USB Flash Drive remain intact even when power is removed from the device. It attaches, physically and electrically, via a Universal Serial Bus (USB) connector, which can be found on any computer built since 1997. The NLS DTB player will also have this kind of connection.

There are five components making up a USB Flash Drive: a USB connector, a controller chip, a flash memory chip, a small printed circuit board (PCB) holding these three components in place, and a plastic shell to hold and protect the PCB.

The USB connector contains the electrical connections needed for the player to communicate with the memory on the cartridge. The flash memory chip holds the DTB itself, which is really a set of specially formatted files. The controller chip controls the communication between the player and the memory. The PCB and shell are there to connect and protect the electronic components.

USB Flash Drives can be purchased off the shelf at any electronics or office supply store. The units used by NLS will be largely the same as these commercial products (in order to reduce cost) but will have two key differences. First, the shell will be customized to carry a large-print or braille label and to fit snugly into the NLS DTB player. This will make the drive appear more like a plug-in cartridge such as the type used with video game systems. Second, the controller chip will be modified to prevent patrons from altering the data stored on the device.

Why USB Flash Drives?

One of the reasons for flash memory's success as a storage product is its availability in standardized formats. Because of this, a digital camera owner can buy any flash memory card that follows the flash memory standard used by his camera.

But of the available flash memory card standards, only one is appropriate for use by blind and physically handicapped individuals: the USB Flash Drive. That is because it is the only standard that does not specify a physical format for the card. Instead, it is standardized only by the characteristics of its connector. All of the other formats are too small to be handled easily by blind or physically handicapped users, and they do not include sufficient surface area to affix a braille label. The USB Flash Drive can be built to any size and shape as long as it has the right connector. NLS plans to produce these cartridges in a format with sufficient size for easy labeling and handling.

Customization does not come at great expense, because the internals and connector of the cartridge, where most of the costs lie, are standard and widely produced. NLS will produce these cartridges in sufficient quantity to ensure that the customized shell adds only a small amount to the overall cost of the unit.

Technology independence

Another useful property of the USB Flash Drive is the measure of technology independence it provides to NLS. Because the cartridge connects to the player using a standard interface and protocol, the memory technology contained in the cartridge can change without the need for any changes to the player or cartridge writers.

If new memory technologies that are more cost effective than flash are developed, NLS can begin to use those inside its cartridges with no modifications to any other aspect of the program. Other flash memory formats would too tightly couple the design of a DTB player to the type of memory used.

By including a controller chip on the USB Flash Drive (see "What is a USB Flash Drive?" above), NLS can implement write-protection so that cartridges cannot be accidentally erased by patrons.


NLS's 2003 Current Strategic Business Plan for the Implementation of Digital Systems ( http://www.loc.gov/nls/businessplan/2003.html) states that the program is feasible if the cost of a memory cartridge is below $10. According to Gartner, prices will be well below that threshold in 2008, when digital distribution is scheduled to begin.

Table 1 and its accompanying chart show actual and projected wholesale costs through 2008 for three sizes of USB Flash Drive.

Table 1: Worldwide USB Flash Drive average selling price 2001-2008 (actual and projected)
  2001 2002 2003 2004 2005 2006 2007 2008
128MB $78.18 $50.16 $29.95 $19.56 $12.75 $7.92 $6.37 $4.74
256MB $156.83 $98.5 $51.11 $34.89 $19.83 $13.71 $9.76 $6.97
512MB $326.34 $196.13 $112.77 $65.89 $35.69 $21.72 $17.91 $11.88

Chart to accompany table 1.

Source: Gartner Dataquest (November 2004); see footnote one

The smallest of these (128MB), which would hold any one of about 75 percent of NLS's titles, is projected to cost less than $5 in 2008.

While this price is higher than a comparable set of blank cassettes, that cost will be offset by reuse of the cartridge. That is, once a title is no longer in high circulation, some or all of the cartridges dedicated to that book can be reused for a different title. In this way, each cartridge can be used for numerous titles throughout its lifetime, amortizing the cost over a longer period.

Cost and capacity floor

Table 2 and its accompanying chart show the average selling prices of the smallest available USB Flash Drives (history from 2001 and projected to 2008). The projections show that while capacities continue to increase, the price of the smallest available part will remain around $5. If these trends continue, the 128MB cartridge will hit this price level within a few years of the rollout of NLS's DTBs. That should be followed by the 256MB and 512MB capacities in subsequent years.

At some point some of these cartridges may be discontinued due to their small size. But, thanks to the choice of the USB Flash Drive standard, this will have no effect on NLS, as the next-smallest size can be used. So long as the price for at least 128MB remains reasonable, the program can continue indefinitely.

Table 2: Worldwide average selling price of smallest available part, 2001-2008 (actual and projected)
  2001 2002 2003 2004; 2005 2006 2007 2008
Cost $11.13 $8.20 $9.51 $5.71 $5.50 $5.62 $5.90 $4.63
Size 8MB 8MB 16MB 16MB 32MB 32MB 64MB 64MB

Chart to accompany table 2.

Number denotes size of smallest available part, MB
Source: Gartner Dataquest (November 2004) see footnote one


With the cartridges circulating from user to user many times per year, it is imperative that they be extremely durable. In the case of flash memory, durability refers to the ability of the cartridge to withstand physical abuse and to retain the data it houses. NLS will be able to control the former through the proper design of its cartridge, and flash memory is very well rated for the latter.

Existing flash-memory varieties, such as CompactFlash and Secure Digital (or SD, a postage stamp-sized card), are already well known for their durability. In a widely publicized test conducted during the summer of 2004 by Digital Camera Shopper magazine, five memory cards for digital cameras were subjected to a set of physical torture tests, including being dipped in cola, run through a washing machine, and run over by a skateboard. All the cards survived all the tests, retaining their data perfectly.

The cartridge format used by NLS will be larger and sturdier than any of those tested and will be designed and manufactured for maximum durability.

SanDisk, a major manufacturer of flash memory products, has assured NLS that other potential hazards such as humidity, shock, vibration, bending and twisting, electromagnetism, and electrostatic discharge are not problematic for this class of products. The specifications for USB connectors call for thousands of insertions, making connector degradation an unlikely source of problems.

Thus it is extremely unlikely that library patrons will damage their DTBs with normal treatment, including spills, falls, and other everyday mishaps.

Most flash memory products are conservatively specified to retain data for ten years within a wide range of temperature and humidity. Actual retention is probably far longer. NLS does not expect that any given DTB title will remain on a cartridge for that long, as all but the most popular titles will be duplicated on demand. Any cartridge that is found to have lost data can easily be restored.

Other concerns

Cost and durability are major concerns when choosing a medium that will go into wide circulation. NLS looked into a number of other potential impediments before selecting the USB Flash Drive.

Write speed

Since NLS will be duplicating DTBs numbering, over time, in the millions, it is important that each duplication operation not be overly time-consuming, even in an automated setting. While the time required to duplicate a book onto a USB Flash Drive depends on a number of factors, the most limiting will be the speed at which information can be transferred into flash memory. This is called "write speed" and is measured in megabytes per second (MB/s).

Fortunately, the write speed of current flash memory technology and of the USB Flash Drives built around it is already sufficient for NLS's needs and is increasing. Today's mainstream devices can be written to at speeds of more than 4MB/s, so an average DTB can be transferred in around thirty seconds. High-end devices accept data at more than twice that speed. Write speeds are increasing quickly, so by 2008 it is likely that the write speed of a mainstream device will have doubled.

One-time costs

NLS cannot use off-the-shelf USB Flash Drives for its DTBs because they are not suitable in size and shape (see above). Off-the-shelf parts would also allow patrons to easily erase, alter, or rewrite the contents of a cartridge. For these reasons NLS will develop a partially customized device. Modifications to the shell and controller chip are necessary.

These modifications will come at a one-time cost. Once the new shell and controller are designed they will probably be useful for the life of the program. NLS will be purchasing sufficient quantities of cartridges to keep any extra manufacturing costs low.

Cost to regional libraries

Low cost will also make it practical for regional libraries and patrons to purchase their own cartridges. NLS is committed to the idea that local libraries continue to be able to produce local content for use with NLS players, so it is vital that blank cartridges be reasonably priced. Library-owned cartridges will be electronically protected so that only the purchaser will be able to reuse them.

NLS has also considered the future of flash memory. All technologies have a limited life span. Flash memory is clearly the most appropriate memory technology for NLS DTBs at present and will remain so for some time. Other nonvolatile memory technologies are under development and may at some point eclipse flash for density, speed, or cost. One such technology, Magnetic Random Access Memory (MRAM), is likely to be flash's successor, but Gartner predicts that it will be another five to ten years before MRAM is a mature technology. See footnote two

Again, the USB Flash Drive insulates NLS from this technology change. Cartridges with MRAM instead of flash could easily be substituted without any impact on the user or the DTB player.

More of a concern is the future of the USB connection itself. USB has been enormously successful in the computer industry and has already gone through a few revisions. These revisions always keep compatibility in mind, ensuring that older devices continue to work with newer revisions of the USB standard. This is likely to continue for many years. Even if it does not, there is no reason NLS cannot continue to use the current USB standard.


The USB Flash Drive is an ideal medium for the distribution of DTBs. It is reasonably priced, durable, easy to handle, customizable, and widely available. It can be quickly and repeatedly read and written to. It is a robust and adaptable medium that lends itself perfectly to both large-scale circulation and efficient shelving for libraries and duplication on demand for individual patrons.

The USB Flash Drive meets all of NLS's requirements for functionality, durability, flexibility, and cost and will serve NLS for many years in the future. It will help take NLS smoothly into the digital era and beyond.


1. "Market Trends: USB Flash Drives, Worldwide, 2001-2008," Joseph Unsworth, November 12, 2004, Gartner, Inc.

2. "Hype Cycle for Semiconductors, 2004," Jim Tully, Richard Gordon, Stanley Bruederle, Paul O'Donovan, Rafe John Graham Ball, and Dean Freeman, June 11, 2004, Gartner, Inc.

Neil Bernstein is an information technology specialist in the Engineering Section of NLS. He has a background in software development and software project management; his graduate studies include signal processing and multimedia networking.

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Posted on 2006-05-30