An Introduction to Infrared Technology: Applications in the Home, Classroom, Workplace, and Beyond ...

Closing the Gap, 1995, Presentation Manuscript

Authors:
Maureen Kaine-Krolak, MSEE, OTR, and Mark E. Novak, BSEE, PE, Trace R&D Center, University of Wisconsin, Madison, WI


Introduction

As next-generation electronic information systems evolve, it is critical that all people have access to the information available via these systems. Examples of developing and future information systems include interactive television, touchscreen-based information kiosks, and advanced Internet programs. Infrared technology, increasingly present in mainstream applications, holds great potential for enabling people with a variety of disabilities to access a growing list of information resources. Already commonly used in remote control of TVs, VCRs and CD players, infrared technology is also being used and developed for remote control of environmental control systems, personal computers, and talking signs.

For individuals with mobility impairments, the use of infrared or other wireless technology can facilitate the operation of information kiosks, environmental control systems, personal computers and associated peripheral devices. For individuals with visual impairments, infrared or other wireless communication technology can enable users to locate and access talking building directories, street signs, or other assistive navigation devices. For individuals using augmentative and alternative communication (AAC) devices, infrared or other wireless technology can provide an alternate, more portable, more independent means of accessing computers and other electronic information systems.

In this presentation/paper, an introduction to wireless communication in general is first presented. A discussion specific to infrared technology then follows, with advantages and disadvantages of the technology presented along with security, health and safety issues. The importance of establishing a standard is also discussed with relevance to the disability field, and future uses of infrared technology are presented.


Wireless Communication

Wireless communication, as the term implies, allows information to be exchanged between two devices without the use of wire or cable. A wireless keyboard sends information to the computer without the use of a keyboard cable; a cellular telephone sends information to another telephone without the use of a telephone cable. Changing television channels, opening and closing a garage door, and transferring a file from one computer to another can all be accomplished using wireless technology. In all such cases, information is being transmitted and received using electromagnetic energy, also referred to as electromagnetic radiation. One of the most familiar sources of electromagnetic radiation is the sun; other common sources include TV and radio signals, light bulbs and microwaves. To provide background information in understanding wireless technology, the electromagnetic spectrum is first presented and some basic terminology defined.

The electromagnetic spectrum classifies electromagnetic energy according to frequency or wavelength (both described below). As shown in Figure 1, the electromagnetic spectrum ranges from energy waves having extremely low frequency (ELF) to energy waves having much higher frequency, such as x-rays.

Description of figure(s) below

[Figure 1 description: The electromagnetic spectrum is depicted in Figure 1. A horizontal bar represents a range of frequencies from 10 Hertz(cycles per second) to 10 to the 18th power Hertz. Some familiar allocated frequency bands are labeled on the spectrum. Approximate locations are as follows. (Exponential powers of 10 are abbreviated as 10exp.)

10 Hertz: extremely low frequency or ELF.
10exp5 Hertz: AM radio.
10exp8 Hertz: FM radio.
10exp10 Hertz: Television.
10exp11 Hertz: Microwave.
10exp16 Hertz: Infrared (frequency range is below the visible light spectrum).
10exp16 Hertz: Visible Light.
10exp16 Hertz: Ultraviolet (frequency range is above the visible light spectrum).
10exp18 Hertz: X-rays.]

A typical electromagnetic wave is depicted in Figure 2, where the vertical axis represents the amplitude or strength of the wave, and the horizontal axis represents time. In relation to electromagnetic energy, frequency is:

  1. the number of cycles a wave completes (or the number of times a wave repeats itself) in one second

  2. expressed as Hertz (Hz), which equals once cycle per second

  3. commonly indicated by prefixes such as

    a. Kilo (KHz) one thousand
    b. Mega (MHz) one million
    c. Giga (GHz) one billion

  4. directly related to the amount of information that can be transmitted on the wave

Description of figure(s) below

[Figure 2 description: A sine wave is depicted in the graph in Figure 2. The horizontal axis of the graph represents time, and the vertical axis of the graph represents amplitude. One cycle (or one complete sine wave) is labeled on the graph.]

Description of figure(s) below

[Figure 3 description: Graphs of three different sine waves are depicted in Figure 3. The horizontal axis, with values ranging from 0 to 1, represents time in seconds. The vertical axis, with values ranging from -1 to 1, represents arbitrary amplitude. The first graph in the figure depicts a sine wave with a frequency of 1 cycle per second. As shown, the energy wave makes a complete cycle from 0 to its maximum positive value, then through to its maximum negative value, then back to 0. The second graph in the figure depicts a sine wave with a frequency of 2 cycles per second. The sine wave therefore makes 2 complete cycles of moving from 0 to its maximum positive value, through to its maximum negative value, and back to 0, in the same time that the wave in the first graph completes 1 cycle. The third graph in the figure depicts a sine wave with a frequency of 3 cycles per second. The sine wave therefore completes 3 full cycles in the same amount of time that the wave in the first graph completes 1 cycle.]

Figure 3 illustrates energy waves completing one cycle, two cycles and three cycles per second. Generally, the higher the range of frequencies (or bandwidth), the more information can be carried per unit of time.

The term wavelength is used almost interchangeably with frequency. In relation to electromagnetic energy, wavelength is:

  1. the shortest distance at which the wave pattern fully repeats itself

  2. expressed as meters

  3. commonly indicated by prefixes such as

    a. Kilo (km) 10exp3
    b. Milli (mm) 10exp-3
    c. Nano (nm) 10exp-9

  4. inversely proportional to frequency

Figure 4 depicts an infrared energy wave and a radio energy wave, and illustrates the two different energy wavelengths. As is expected based on the electromagnetic spectrum, the infrared wave is higher frequency and therefore shorter wavelength than the radio wave. Conversely, the radio wave is lower frequency and therefore longer wavelength than the infrared wave. Anyone who has listened to the radio while driving long distances can appreciate that longer wavelength AM radio waves carry further than the shorter wavelength FM radio waves.

Description of figure(s) below

[Figure 4 description: Figure 4 depicts a radio frequency energy wave superimposed upon an infrared energy wave, and illustrates the inverse relationship between frequency and wavelength. The infrared energy wave completes nearly 5 and a half cycles in the time that the radio frequency wave completes 2 cycles. The wavelengths of the infrared wave and the radio wave are labeled, and the infrared wavelength is less than half the wavelength of the radio wave.]

Other terms commonly used in describing wireless communication include transmitter, receiver, and transceiver. In any type of wireless technology, information must be sent (or transmitted) by one device and captured (or received) by another device. The transmitter takes its input - a voice or stream of data bits for example, creates an energy wave that contains the information, and sends the wave using an appropriate output device. As an example, a radio transmitter outputs its energy waves using an antenna, while an infrared transmitter uses an infrared light- emitting diode (LED) or laser diode. The electromagnetic energy waves are captured by the receiver, which then processes the waves to retrieve and output the information in its original form. Any wireless device having the circuitry to both transmit and receive energy signals is referred to as a transceiver. Depending on the communication protocol being used, a device may be capable of only transmitting or receiving information at one time, or it may be capable of both transmitting and receiving information at the same time.

The above described terminology is relevant in all forms of wireless communication, regardless of the band of electromagnetic energy (radio, infrared, etc.) being used. Although radio and ultrasound waves have frequent application in wireless communication, the remainder of the presentation/paper is devoted more specifically to infrared (IR) technology. Infrared technology is highlighted because of its increasing presence in mainstream applications, its current and potential usage in disability-related applications, and its advantages over other forms of wireless communication.


Infrared Technology

As depicted in Fig. 1, infrared radiation is the region of the electromagnetic spectrum between microwaves and visible light. In infrared communication an LED transmits the infrared signal as bursts of non-visible light. At the receiving end a photodiode or photoreceptor detects and captures the light pulses, which are then processed to retrieve the information they contain. Some common applications of infrared technology are listed below.

  1. Augmentative communication devices
  2. Car locking systems
  3. Computers
    a. Mouse
    b. Keyboards
    c. Floppy disk drives
    d. Printers
  4. Emergency response systems
  5. Environmental control systems
    a. Windows
    b. Doors
    c. Lights
    d. Curtains
    e. Beds
    f. Radios
  6. Headphones
  7. Home security systems
  8. Navigation systems
  9. Signage
  10. Telephones
  11. TVs, VCRs, CD players, stereos
  12. Toys

Infrared technology offers several important advantages as a form of wireless communication. Advantages and disadvantages of IR are first presented, followed by a comparative listing of radio frequency (RF) advantages and disadvantages.


IR Advantages:

  1. Low power requirements: therefore ideal for laptops, telephones, personal digital assistants
  2. Low circuitry costs: $2-$5 for the entire coding/decoding circuitry
  3. Simple circuitry: no special or proprietary hardware is required, can be incorporated into the integrated circuit of a product
  4. Higher security: directionality of the beam helps ensure that data isn't leaked or spilled to nearby devices as it's transmitted
  5. Portable
  6. Few international regulatory constraints: IrDA (Infrared Data Association) functional devices will ideally be usable by international travelers, no matter where they may be
  7. High noise immunity: not as likely to have interference from signals from other devices


IR Disadvantages:

  1. Line of sight: transmitters and receivers must be almost directly aligned (i.e. able to see each other) to communicate
  2. Blocked by common materials: people, walls, plants, etc. can block transmission
  3. Short range: performance drops off with longer distances
  4. Light, weather sensitive: direct sunlight, rain, fog, dust, pollution can affect transmission
  5. Speed: data rate transmission is lower than typical wired transmission


RF Advantages:

  1. Not line of sight
  2. Not blocked by common materials: can penetrate most solids and pass through walls
  3. Longer range
  4. Not light sensitive
  5. Not as sensitive to weather/environmental conditions


RF Disadvantages:

  1. Interference: communication devices using similar frequencies - wireless phones, scanners, wrist radios and personal locators can interfere with transmission
  2. Lack of security: easier to "eavesdrop" on transmissions since signals are spread out in space rather than confined to a wire
  3. Higher cost than infrared
  4. Federal Communications Commission(FCC) licenses required for some products
  5. Lower speed: data rate transmission is lower than wired and infrared transmission
In addition to the above noted advantages and disadvantages of IR and RF technology, there are other issues that are also pertinent to the consideration of wireless communication systems. Health, safety and security issues are now discussed.


Health Risks

Imagine for a moment going about your daily routine without electricity. You probably awoke to an electric clock radio/alarm, showered under warm water supplied via an electric hot water heater, drank a couple of cups of coffee from your automatic electric coffee maker, listened to the weather on the electric powered TV or radio - and the list goes on and on. We live in an electrical environment!

Electricity is all around you and while you cannot see electricity, you can certainly appreciate the results. However, any time electric current travels through a wire, the air, or runs an appliance, it produces an electromagnetic field. It is important to remember that electromagnetic fields are found everywhere that electricity is in use. While researchers have not established an ironclad link between the exposure to electromagnetic fields and ailments such as leukemia, the circumstantial evidence concerns many people.

The evidence also suggests that we need to use some common sense when dealing with electricity. In scientific terms, your body can act as an antenna, as it has a higher conductivity for electricity than does air. Therefore, when conditions are right you may have experienced a small "tingle" of electric current from a poorly grounded electric appliance. As long as these currents are very small there isn't much danger from electric fields, except for potential shocks. Your body, however, also has a permeability almost equal to air, thus allowing a magnetic field to easily enter the body. Unfortunately your body cannot detect the presence of a strong magnetic field, which could potentially do much more harm.

In terms of wireless technology, there are no confirmed health risks or scientific dangers from infrared or radio frequency, with two known exceptions:

  1. point-to-point lasers which can cause burns or blindness
  2. prolonged microwave exposure which has been linked to cancer and leukemia
Therefore, most health concerns related to electromagnetic fields are due to electricity in our day-to-day use, such as computer monitors and TVs. These dangers, if any, are already in the home and work place, and the addition of wireless technology should not be seen as an exceptional risk. We might be rightfully worried or concerned about the electric power grid two blocks from our home or school, but at the same time, we sleep each night with our head only a few feet from an AC powered clock radio, which may be far worse due simply to proximity. We might be also be worried about the magnetic radiation or magnetically induced electrical fields which surround us from the fluorescent light fixtures and high voltage, high frequency lighting we sit under at work and at home. The real danger, however, is that we normally position ourselves too close to the electromagnetic field source (computer monitor, TV, etc.). Remember that the strength of the electromagnetic field (EMF) decreases as the square of the distance from the field source. Therefore, if we are 2 meters away from the source, the EMF strength is reduced to 1/4, but if we move 8 meters away from the source, the EMF strength is reduced to 1/64 of its original strength.


Safety

There are a few things you can do to make your home and work environment a safer "electronic" place. The first thing to consider when possible is to buy Federal Communications Commission (FCC) Class B rated equipment. The FCC classifies computer equipment for its potential to generate radio frequency pollution. Class B emits less radio frequency pollution than Class A, and is more suitable for the residential environment. Unfortunately, while Class B emits less radio frequency pollution, there is nothing in the FCC classes regarding magnitude or level of the pollution.

Other potential risks exist in high voltage (e.g. power) components such as display monitors, computer power supplies, etc. If possible select low power units, shielded units, etc. and operate them at lower resolutions. For example, VGA resolution has a lower refresh scan rate than SVGA, and thus lower magnetic field pollution. If you are adding internal cards to your computers, don't tamper with the computer by removing any internal shielding, covers, etc. Any metal shielding inside your computer was probably put there for a purpose, although to you it may look like a harmless spacer!

If you are really concerned, you can purchase formal safety testing tools or hire a consultant to do formal testing for EMF. There are also cheap tools you can utilize to test for the presence of strong radio or magnetic fields. For example, the presence of a strong magnetic field will deflect a compass needle from pointing north, or the presence of a strong radio frequency field will distort an AM radio's ability to clearly tune in a station. Simple tools like these can be used to screen for strong EMF.


Security

Electromagnetic frequencies currently have little legal status for protection and as such, can be freely intercepted by motivated individuals. This doesn't mean wireless transmission is easily breached, as security varies by the type of wireless transmission method. As presented earlier in the advantages and disadvantages of infrared versus radio frequency transmission, what might be considered an advantage to one method for transmission could turn out to be a disadvantage for security. For example, because infrared is line-of-sight it has less transmission range but is also more difficult to intercept when compared to radio frequency. Radio frequency can penetrate walls, making it much easier to transmit a message, but also more susceptible to tapping.

A possible solution to security issues will likely be some form of data encryption. Data encryption standards (DES) are also being quickly developed for the exchange of information over the Internet, and many of these same DES will be applied to wireless technology.


Importance of Standards

Several of the wireless devices demonstrated during the presentation (see Appendix A) have benefited to some degree from standardization. For example, a universal IR remote was once priced at roughly $100.00. It is now possible, for under $15.00, to purchase a universal remote that will learn the IR codes for all of your electronic appliances - not just the TV or VCR. Another example of a device that has benefited from standardization is the Macintosh IR mouse. The compatibility of this mouse to the Apple Desktop Bus (ADB) Standard has certainly contributed to its inexpensive price and availability. As you look around the exhibit hall, think of all the assistive devices that have proliferated due to the ADB (IntelliKeys, Ke:nx, etc.). Additionally, the X10 devices that were demonstrated in the presentation not only rely on but have benefited from the 60 HZ AC standard which applies to most of North America. As a result these devices are now numerous and inexpensive. One final example demonstrating the importance of standards is the relationship of augmentative alternative communication (AAC) devices to the General Input Device Emulating Interface (GIDEI) standard. Any AAC device programmed to use the GIDEI protocol can access any PC or Macintosh running either the DOS, Windows, or Macintosh version of SerialKeys. The collaboration of the rehabilitation field to create the GIDEI standard has allowed AAC users to access multiple computers without the need to reprogram their devices or purchase expensive, proprietary hardware.

Likewise, there is an urgent need to develop standards regarding the use of wireless technology in accessing electronic appliances of all kinds. Without such a standard, it may be difficult if not impossible for those using assistive devices to communicate with all available information systems. Examples of current or developing appliances which can or may potentially be accessed via wireless technology include:

  1. ATMs
  2. Information Kiosks
  3. Building Directories
  4. TV Set Top Boxes
  5. Bus Stops (Electronic Interactive)
  6. Fare Machines (ticket machines, etc.)
  7. Home Appliances (especially touchscreens)
  8. Informational Telephones, Screen Based Telephones
  9. POS (point of sale) equipment
  10. Home environmental controls
  11. Home security systems
  12. Whiteboards, for classroom / interactive office use
  13. Games and entertainment
With the need for a standard in mind, the Trace Center has initiated a Universal "Disability" IR link working group, as part of the Center's Info-Curbcuts Project. The group is working to accomplish the following:
  1. Develop a bi-directional universal disability infrared link where by individuals with different disabilities equipped with specialized access devices could both locate and interact with various electronic information systems.

  2. Develop guidelines or a "standard protocol" for this universal disability IR link, building upon accepted industry standards such as the Infrared Data Association (IrDA).

  3. Advocate and work closely with product developers to get the ideas and "standard protocol" for this universal disability IR link incorporated into as wide a variety of mainstream electronic devices as possible.

  4. Cooperate with, or at the very least not interfere with, other IR and RF technologies such as Talking Signs, etc.

    The Universal Disability IR Link will have several requirements:

    a. The link must always be looking for a connection (so that the person with a disability can approach a system and have the system recognize them without requiring the person to activate the link from the system).
    b. There should be some type of security provided.
    c. The link must not interfere with other IR uses.
    d. The link must not be blocked by other IR uses.
    e. The link must be bi-directional.
    f. The link should support talking sign technologies or at a minimum not conflict with them.
    g. The user should always be considered in control of the link. (The user makes a request via the link, and the system then responds via the link. The system may respond with a choice for the user to make, but it is still the user in control.)

To meet these requirements, a "Straw Man" protocol is being proposed (see Appendix B). The Trace Center Universal "Disability" IR link working group would appreciate any comments and feedback regarding this proposal.

In addition, the IR link working group has a discussion listserve on line at the Center. If you wish to join, please send e- mail to <listproc@trace.wisc.edu>. Do not use a heading or signature field in your e-mail. In the body of your message, simply type:

subscribe irlink-l <yourfirstname> <yourlastname>

(Note, the <> signs are for clarification only, do not include them in your e-mail.)

Contact information for the authors:

Trace Research & Development Center
S-151 Waisman Center
1500 Highland Avenue
Madison, Wisconsin 53705-2280
Telephone: 608-262-6966
TDD: 608-263-5408
FAX: 608-262-8848


References

1. Nemzow, Martin. 1995. Implementing Wireless Networks. New York: McGraw-Hill.

2. Davis, Peter T. and McGuffin, Craig R. 1995. Wireless Local Area Networks: Technology, Issues, and Strategies. New York: McGraw-Hill.

3. Resnick, Robert and Halliday, David. 1988. Fundamentals of Physics: Third Edition Extended. Toronto: John Wiley & Sons.

4. FitzGerald, Jerry and Eason, Tom S. 1978. Fundamentals of Data Communications. New York: John Wiley & Sons.

5. Goldberg, Lee. Infrared Data Transmission: The Missing Link? Electronic Design. April 17, 1995:47-64.

6. Cremer, Mike. An Introduction to the IrDA Protocols. PDA Developers 2.6. Nov/Dec, 1994:35-39.

7. Weeder, Terry J. Remote Control Adapter . Electronics Now. August 1995:41-49,83.


Appendix A

Products demonstrated in the presentation include:

  1. Wireless Keyboard
    Alphameric
    1640 Fifth Street, Suite 224
    Santa Monica, CA 90401
    Tel: (310) 393-7028 Fax: (310) 393-6040
    $125.00

  2. JetEye LT IR Portable Computer File Transfer Kit
    Extended Systems
    5777 N. Meeker Ave.
    Boise, ID 83711
    Tel: (800) 235-7576
    $99.00

  3. Tykriphone
    Tykris Inc.
    421 Nugget Ave., Unit #5
    Scarborough, Ont. M1S4L8
    Tel: (416) 609-2540 Fax: (416) 609-2363
    $1300.00

  4. GEWA Infra-Link Speaker-Telephone
    Infra-Link, Inc.
    P.O. Box 1008
    Portland, OR 97224
    Tel: (800) 395-3596 Fax: (503) 598-7531
    $695.00

  5. Cordless Dyna Mouse
    Spec Research Inc.
    19433 San Jose Ave.
    City of Industry, CA 91789
    Tel: (909) 595-1258
    $31.00

  6. MouseMan Cordless
    Logitech, Inc.
    6505 Kaiser Drive
    Fremont, CA 94555
    Tel: (510) 795-8500
    $89.95

  7. Talking Signs
    Talking Signs, Inc.
    812 North Blvd.
    Baton Rouge, LA 70802
    Tel: (504) 344-2812 Fax: (504) 344-2811
    Transmitters...$350.00 Receivers...$250.00*
    *Special price for blind and low visioned individuals

  8. X-10 Powerhouse IR Command Center
    X-10 (USA) Inc.
    185A LeGrand Ave.
    Northvale, NJ 07627
    Tel: (201) 784-9700
    (sold by Radio Shack)
    $39.95

  9. Plug'n Power Appliance Module
    Radio Shack
    Divison of Tandy Corp.
    Ft. Worth, TX 76102
    Tel: (800) 950-7557
    $13.99

  10. Universal Remote
    Radio Shack
    Divison of Tandy Corp.
    Ft. Worth, TX 76102
    Tel: (800) 950-7557
    $29.99

  11. U-Control
    Words+, Inc.
    40015 Sierra Highway, Bldg. B-145
    Palmdale, CA 93550
    Tel: (800) 266-8500
    $495.00

  12. Laplink Remote Access
    Traveling Software Inc.
    18702 North Creek Parkway
    Bothell, WA 98011
    Tel: (206) 483-8088
    $269.00

  13. Synchro Plus
    Traveling Software Inc.
    18702 North Creek Parkway
    Bothell, WA 98011
    Tel: (206) 483-8088
    $99.95

  14. Dynavox
    Sentient Systems Technology, Inc.
    2100 Wharton Street, Suite 630
    Pittsburgh, PA 15203
    Tel: (800) 344-1778
    $3995.00

  15. Dynavox II
    Sentient Systems Technology, Inc.
    2100 Wharton Street, Suite 630
    Pittsburgh, PA 15203
    Tel: (800) 344-1778
    $5995.00

  16. Light-up Pumpkin
    Walgreens
    $9.99


Appendix B

A "Straw Man" PROTOCOL (what travels through the air) FOR THE UNIVERSAL DISABILITY IR LINK PROJECT Introduction:

Based on input to date and our past meetings, the following "straw man" protocol has been developed to give us a reference point, and a point to begin discussions. This does not include a bit of hand-shaking that would have to take place up front to establish a secure connection, etc.

Objectives:

To provide the information and control necessary to allow people with different disabilities to access and use different electronic information appliances effectively.

To create the smallest and simplest set of commands that will provide the greatest flexibility.

To implement this in such a way that it could ride on top of or be a standard protocol within the IrDA protocol.

Uses:

An individual who is blind could use a separate device (e.g., personal computer with voice or Braille) to access the device. They would be able to find out what was on screen at any point in time (text and buttons or controls). They could have the information displayed for them on their remote device and activate the controls, also from their remote device. (This would also work in the same manner for a person who is deaf- blind.)

An individual with a physical disability who is unable to reach or use the standard controls (e.g., someone with high spinal cord injury who uses a sip and puff controlled wheelchair) could view the information on the regular screen or their personal assistive device, and use the assistive device to activate the buttons or controls.

NOTE: The IR link is NOT intended to replace direct access to Information Appliances (i.e. the ability of people who are blind or have other disabilities to use the appliances directly). This is still the goal. However, we as a field do not yet know how to practically make appliances that can be accessed directly (e.g. without assistive devices) by everyone, (e.g. people who are deaf-blind or who use sip and puff or eye gaze to control appliances). The IR link allows a mechanism for these people (and others who prefer) to access information systems using their personal assistive devices. It may also allow an inexpensive way to add access to a wider array of products.

PART I: Protocol for communication from the "aid" to the "information device"

THERE ARE 3 COMMANDS THAT CAN BE SENT BY AN ASSISTIVE DEVICE ("AID")

SHORT-NAME COMMAND DESCRIPTION OF COMMAND
1. RESET #R <ret> reset system to start (local home)
2. LIST #L <ret> send a list of information and action items
3. ACTIVATE #item reference number <ret>
or "verbal name of item" <ret>		 activate this item

NOTE: when the user sends the "list" command, the device may optionally display the names or reference numbers next to the items on the screen to facilitate access by users who can see the screen but who must use an alternate device connected via the IR-l ink to "push" the buttons etc.

PART II: Protocol for communication from the "information device" to the "aid"

ALL INFORMATION SENT BY THE "INFORMATION DEVICE" IS IN RESPONSE TO COMMANDS FROM THE USER (AID)

In response to RESET

In response to LIST

In response to ACTIVATE

Details on the Description table sent in response to LIST command

END of strawman protocol...

BACK to UDIRCL PAPERS