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Institute of Medicine (US) Committee on Evaluating Clinical Applications of Telemedicine; Field MJ, editor. Telemedicine: A Guide to Assessing Telecommunications in Health Care. Washington (DC): National Academies Press (US); 1996.

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Telemedicine: A Guide to Assessing Telecommunications in Health Care.

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BGlossary* and Abbreviations


A · B · C · D · E · F · H · I · L · M · N · O · P · R · S · T · U · V · W


Advanced Research Projects Agency (ARPA)

The DOD agency that created the computer network that evolved into the Internet.


Electronic devices used to boost the strength of a signal as it passes along a communications channel.

Analog signal

A continuous electrical signal in the form of waves that vary as the source of the information varies (e.g., as the contrast in an image varies from light to dark).


The selection, design, and interconnection of the physical components of a computer system.

Asynchronous communication

Two-way communication in which there can be a time delay between when a message is sent and when it is received.

Asynchronous transfer mode (ATM)

A type of switching that is expected to bridge the gap between packet and circuit switching. ATM uses packets called cells that are designed to switch cells so fast that there is no perceptible delay.


Two-way electronic voice communication between two or more people at separate locations.


The use of passwords, keys, and other automated identifiers to verify the identity of the person sending or receiving information.

Automated data collection

Direct transfer of physiological data from monitoring instruments to either a bedside display system or a computer-based patient record.



A high-capacity communications channel that carries data accumulated from smaller branches of the computer or telecommunications network.


A measure of the information carrying capacity of a communications channel; a practical limit to the size, cost, and capability of a telemedicine service.


A unit of digital transmission signaling speed of information transmission; the highest number of single information elements (bits) transferred between two devices (such as modems or fax machines) in one second.

Bell Operating Companies (BOCs)

Grouped under the seven Regional BOCs (see RBOC).


Binary digit, the smallest possible unit of information making up a character or a word in digital code processed by computers.


The number of binary digits transmitted per second in a data communication system.


Communications (e.g., broadcast television, microwave, and satellite) capable of carrying a wide range of frequencies; refers to transmission of signals in a frequency-modulated fashion, over a segment of the total bandwidth available, thereby permitting simultaneous transmission of several messages.


A set of eight bits.


Cable television (CATV)

A transmission system that distributes broadcast television signals and other services by means of a coaxial cable.

Central processing unit (CPU)

A unit of a computer that includes circuits controlling the interpretation and execution of instructions.


A radio frequency assignment made according to the frequency band being used and the geographic location of the sending/receiving sites.

Circuit Switched Network

A network that temporarily connects two or more channels between two or more points to provide the user with exclusive use of an open channel to exchange information, also called line switching and dial-up service.

Clinical information system

Hospital-based information system designed to collect and organize data related to the care given to a patient, rather than administrative data.

Coaxial cable

Transmission wire(s) covered by an insulating layer, a shielding layer, and an outer jacket; used for data, voice, and video transmissions; can transmit either broadband (several signals) or baseband (one signal).


A "code/decode" electrical device that converts an analog electrical signal into a digital form for transmission purposes and then converts it back at the other end.

Common carrier

A telecommunications company regulated by government agencies that offers communications relay services to the general public via shared circuits, charging published and nondiscriminatory rates.

Communication multiplexer

A device that allows data from multiple, lower speed communication lines to share a single higher speed communication path.


The ability for computer programs and computer readable data to be transferred from one hardware system to another without losses, changes, or extra programming.

Compressed video

Video images that have been processed to reduce the amount of bandwidth needed to capture the necessary information so that the information can be sent over a telephone network.

Computer-based patient record (CPR)

A compilation in electronic form of individual patient information that resides in a system designed to provide access to complete and accurate patient data, alerts, reminders, clinical decision support systems, links to medical knowledge, and other aids.

Computer conferencing

Group communications through computers, or the use of shared computer files, remote terminal equipment, and telecommunications channels for two-way, real-time communication.


Data compression

Processing data to reduce storage and bandwidth requirements. Some compression methods result in the loss of some information, which may or may not be clinically important.

Data repository

The component of an information system that accepts, files, and stores data from a variety of sources.

DAX (digital exchange)

A computerized digital cross connection that allows specific channels from high capacity lines to split out separately and be redirected.

Dedicated line

Permanent connection between two telephones or PBXs (see private branch exchange, below); the signal does not need to be switched.


Discrete signals such as those represented by bits as opposed to continuously variable analog signals. Digital technology allows communications signals to be compressed for more efficient transmission.

Digital Imaging and Communication in Medicine (DICOM)

A standard for communications among medical imaging devices.


Conversion of analog into digital information.

Direct broadcast satellite (DBS)

A satellite designed with sufficient power so that inexpensive earth stations, or downlinks, can be used for direct residential reception.

Direct digital imaging

Involves the capture of digital images so that they can be electronically transmitted.


The path from a satellite to the Earth stations that receive its signals.


A digital carrier capable of transmitting 1.544 Mbps of electronic information. Also known as T1; the general term for a digital carrier available for high-value voice, data, or compressed video traffic.


A carrier of 45 Mbps bandwidth. One DS3 (also known as T3) channel can carry 28 DS1 channels.


A transmission system allowing data to be transmitted in both directions simultaneously.


Earth station

The ground equipment, including a dish and other electronics needed to receive and/or transmit satellite telecommunications signals.

Electronic data interchange (EDI)

The sending and receiving of data directly between trading partners without paper or human intervention.


The rearrangement of the "bit" stream of a previously digitally encoded signal in a systematic fashion to make it unrecognizable until restored by the necessary authorization key. This technique is used for securing information transmitted over a communication channel with the intent of excluding all other than the authorized receivers from interpreting the message.

Equal access

Ability to choose between the different long-distance carriers.


Fiber distributed data interface (FDDI)

A high-speed fiber optic network which has state-of-the-art bandwidth.

Fiber optics

Hair-thin, flexible glass rods encased in cables that use light to transmit audio, video, and data signals.

Film digitizer

A device that allows scanning of existing static images so that the images can be stored, manipulated, or transmitted in digital form.

Filmless radiology

Use of devices that replace film by acquiring digital images and related patient information and transmit, store, retrieve, and display them electronically.


Computer hardware and software that lock unauthorized communications between an institution's computer network and external networks.

Frame Relay

A streamlined process of sending and acknowledging transmitted packets of data which improves the rate of data transfer compared to previous transmission protocols.

Freeze-frame (Slow scan)

A method of transmitting still images over standard telephone lines at a rate of one every 8 to 30 seconds.


The rate at which an electromagnetic signal alternates, reported in Hertz.

Full duplex

A communication channel over which both transmission and reception are possible at the same time.

Full-motion video

A standard video signal requiring 6MHz (megahertz) in analog format and 45Mbps when encoded digitally.



A communication channel over which both transmission and reception are possible, but only in one direction at a time.


Physical equipment used in data processing, as opposed to computer programs and associated documentation.

Hard wired

A communication link that permanently connects two devices.

Health Care Information Infrastructure (HCII)

A subset of the National Information Infrastructure (see below).

Health Level-7 Data Communications Protocol (HL-7)

Defines standards for transmitting billing, hospital census, order entries, and other health-related information.


A measure of the number of complete cycles made by an analog signal in a given time period.

High-definition television (HDTV)

An advanced television system that produces video images as clear as high-quality photographs.

High Performance Computing and Communications program (HPCC)

A federal, coordinated, interagency research and development effort designed to accelerate the availability and utilization of the next generation of high performance computers and networks.


Image processing

Use of algorithms to modify data representing an image, usually to improve diagnostic interpretation.

Independent telephone company

A local exchange carrier that is not part of the BOCs (Bell Operating Companies, see above), often cooperative in rural areas.


The application of computer science and information science to the management and processing of data, information, and knowledge.

Integrated circuit

A solid state microcircuit consisting of interconnected semiconductor elements diffused into a single device.

Integrated services digital network (ISDN)

A digital telecommunications technology that allows for the integrated transmission of voice, data, and video; a protocol for high-speed digital transmission.

Interexchange carrier (IXC)

Also known as a long-distance carrier, a telephone company that carries long-distance calls.


The boundary between two hardware or software systems across which data are transferred.


The largest international computer network, linking computers and computer networks from colleges and universities, government agencies, institutions, and commercial organizations worldwide.


Leased lines (Dedicated lines)

Lines rented from a telephone company for the exclusive use of a customer.

Local access transport area (LATA)

Local telephone service areas created by the divestiture of the Regional Bell Operating Companies (RBOCs, see below) formerly associated with AT&T.

Local area networks (LANs)

Private networks that facilitate the sharing of information and computer resources by members of a specific group.

Local exchange carrier (LEC)

Carrier providing local services to customers within a LATA (see above).


Medical informatics

The combination of computer science, information science, and medicine designed to assist in the management and processing of data to support the delivery of health care.

Message switching

A message (image or text) divided into many parts that are then transmitted separately to the receiver where they are put back together to form the message.


High-frequency radiowaves used for point-to-point communication of audio, video, and data signals; its spectrum is generally above 2 GHz (gigahertz).


A modulator/demodulator, this device converts digital information into analog form for transmission over a telecommunications channel and reconverts it to digital form at the point of reception.


Combination of many low-capacity communications channels into one high-capacity communications channel by interleaving the various channels in discrete time of frequency slices.



A telecommunications medium that uses (relatively) low-frequency signals, not exceeding 1.544 Mbps.

National Information Infrastructure (NII)

The integration of hardware, software, and skills that will make it easy and affordable to connect people with each other, with computers, and with a vast array of services and information resources.


A set of nodes, points, or locations connected by means of data, voice, and video communications for the purpose of exchange.


A branching or exchange point for networks.


Open system

A system that permits connection to a variety of other systems or technologies.

Optical character recognition (OCR)

Automated scanning and conversion of printed characters to computer-based text.



A short block of data containing information on its source, content, and destination that is transferred in a packet switched network.

Packet switched network (PSN)

Transmitted data broken into small packets so that each can be sent over a different route if there is extensive network traffic.

Packet switching

The process of transmitting digital information by means of addressed packets so that a channel is occupied only during the transmission of the packet.

Peripheral equipment

In a data processing system, any equipment, distinct from the central processing unit, that may provide the system with outside communication or additional facilities.

Picture archiving and communications system (PACS)

A system that acquires, transmits, stores, retrieves, and displays digital images and related patient information from a variety of imaging sources and communicates the information over a network.


The smallest displayable area on a computer screen; the fundamental picture element of a digital image.

Private branch exchange (PBX)

A private telephone exchange that serves a particular organization and has connections to the public telephone network.


Internal telephone systems located on the premises of many large offices.

Public switched telephone network (PSTN)

The public telephone network.


Real time

The capture, processing, and presentation of data at the time the data is originated.

Regional Bell Operating Company (RBOC)

One of the seven regional companies formed by the AT&T divestiture.


A bidirectional device used to amplify or regenerate signals.


Spatial resolution is the ability to distinguish between adjacent structures. Contrast resolution is the ability to distinguish between shades of gray.


The assignment of a communication path.

Rural area networks (RANs)

Shared-usage networks, configured to include a wide range of users in rural communities, such as educational, health, and business entities.



An electronics retransmission device serving as a repeater, placed in orbit for the purpose of receiving and retransmitting electromagnetic signals.

Signaling System 7 (SS7)

A recent development in control systems for the public telephone network making telephone call processing faster and more efficient and making more services available to consumers.

Slow scan video

A device that transmits and receives still video pictures over a narrow telecommunications channel.


Transmission of static images or audio-video clips to a remote data storage device, from which they can be retrieved by a medical practitioner for review and consultation at any time, obviating the need for the simultaneous availability of the consulting parties and reducing transmission costs due to low bandwidth requirements.

Structured data entry

A data collection technique that constrains the language and format of clinical descriptions for the purpose of ensuring uniform, unambiguous, interchangeable messages.


A mechanical or solid state device that opens or closes circuits, changes operating parameters, or selects paths or circuits on a space or time division basis.

Switched line

Communication link for which the physical path, established by dialing, may vary with each use.

Switched network

A type of system where each user has a unique address that allows the network to connect any two points directly.

Synchronous transmission

The process by which bits are transmitted at a fixed rate with the transmitter and receiver synchronized, eliminating the need for start/stop elements, thus providing greater efficiency.



See DS1.


See DS3.


Price structures for communication facilities set forth by federal or local governments, intended to allow telephone companies (LATA, see local access transport area, above) a fair rate of return on their capital investments.


Series of transmission systems using pulse code modulation technology at various channel capacities and bit rates to send digital information over telephone lines or other transmission medium.


The use of wire, radio, optical, or other electromagnetic channels to transmit or receive signals for voice, data, and video communications.


Interactive electronic communication between two or more people at two or more sites, which make use of voice, video, and/or data transmission systems.


Audio, video, or other electronic consultation between two or more geographically separated clinicians.


The detection of a disease by evaluating data transmitted to a receiving station from instruments monitoring a distant patient.


The use of computer-based information processing in telecommunications and the use of telecommunications to allow computers to transfer programs and data to one another.


The use of electronic and telecommunications technologies to provide and support health care when distance separates the participants.


The use of audio, video, and other telecommunications and electronic information processing technologies to provide individual guidance or instruction, for example, involving a consultant guiding a distant clinician in a new medical procedure.


The use of audio, video, and other telecommunications and electronic information processing technologies to monitor patient status at a distance.


The use of robotic and other devices that allow a person (e.g., a surgeon) to perform a task at a remote site by manipulating instruments (e.g., lasers or dental handpieces) and receiving sensory information or feedback (e.g., pressure akin to that created by touching a patient) that creates a sense of being present at the remote site and allows a satisfactory degree of technical performance (e.g., dexterity).


A broadcasting service using several otherwise unused scanning lines (vertical blanking intervals) between frames of TV pictures to transmit information from a central database to receiving television sets.

Terrestrial carrier

A telecommunications transmission system using land-based facilities.


The amount of data that can be transmitted over a network in a given period of time.

Tie line

A leased or dedicated telephone circuit provided by common carriers that links two points together without using the switched telephone network (see trunk, below).

Transmission control protocol/Internet protocol (TCP/IP)

A communications protocol governing data exchanged on the Internet.

Transmission speed

The speed at which information passes over the line; defined in either bits per second (bps) or baud (see above).


A microwave repeater (receiver and transmitter) in a satellite that receives signals being sent from Earth, amplifies them, and sends them back down to Earth for reception purposes.


A large-capacity, long-distance channel used by common carriers to transfer information between its customers.

Twisted pair

The most prevalent type of medium in PSTN's (public switched telephone network, see above) local loops, insulated copper wires are wrapped around each other to cancel the effects of electrical noise. It can transmit voice, data, and low-grade video.



The path/link from a transmitting Earth station to the satellite.



The extent to which an observed situation reflects the true situation.

Video conferencing

Real-time, usually two-way transmission of digitized video images between two or more locations.

Video frame grabber

A device that converts an analog video signal into a set of digital values.

Virtual circuit

Packet switched network facilities that give the appearance of an actual end-to-end circuit.

Virtual reality

A computer-based technology for simulating visual, auditory, and other sensory aspects of complex environments.

Voice grade channel

A telephone circuit of sufficient bandwidth to carry signals in the voice frequency range of 300 to 3,400 Hertz.

Voice switching

An electrical technique for opening and closing a circuit in response to the presence or absence of sound.


Wide area network (WANs)

Data communication networks that provide long-haul connectivity between separate networks located in different geographic areas.

Wide area telephone service (WATS)

A telephone service with a flat rate for measured bulk-rate, long-distance services provided on an incoming or outgoing basis.

World Wide Web (WWW)

Internet system for worldwide hypertext linking of multimedia documents.


A functional grouping of computer hardware and software (e.g., monitor, keyboard, hard drive) for individual uses such as word, information, and image processing.



Agency for Health Care Policy and Research


Area Health Education Center


American Medical Association


American Medical Informatics Association


American National Standards Institute


Advanced Research Projects Agency, DOD


American Standard Code for Information Interchange


American Telemedicine Association


Asynchronous transfer mode


Bell Operating Companies


Cable television


Compact disk, read-only memory




Computer-based patient record


Central processing unit


Direct broadcast satellite


Department of Health and Human Services


Digital Imaging and Communications in Medicine


Department of Defense


Department of Veterans Affairs


Electronic data interchange


Health Care Financing Administration


Hospital Information System


Health Level-7 Data Communications Protocol


High Performance Computing and Communications


Institute of Medicine


Integrated services digital network


Joint Commission on Accreditation of Health care Organizations


Local area network


Long distance carrier


Local exchange carrier


Magnetic Resonance Imaging


National Academy of Sciences


National Aeronautics and Space Administration


National Institutes of Health


National Information Infrastructure


National Institute of Standards and Technology


National Library of Medicine


National Research Council


National Science Foundation


Office of Rural Health Policy


Office of Technology Assessment


Picture archiving and communications systems


Private branch exchange


Physician hospital organization


Preferred provider organization


Packet switched network


Public switched telephone network


Rural area network


Regional Bell Operating Company


Radiology Information System


Transmission control protocol/Internet protocol


Telemedicine Information Exchange


World area network


World area telephone service


World Wide Web



Sources for these definitions, in addition to members of the committee, include ORHP, 1993; Greberman et al., 1994; OTA 1995; and the Telemedicine Glossary developed by the State University of New York Health Science Center at Syracuse (http://www​.hscsyr.edu​/wwwserve/telemedicine/glossary.html)

Copyright © 1996, National Academy of Sciences.
Bookshelf ID: NBK45447


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