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Alphabetical Listing

Analog

Pertaining to representation by means of continuously variable physical quantities, such as varying voltages, frequencies, etc.

Asynchronous

 
1. Having a variable time interval between successive bits, character, or events. In asynchronous data transmission, each character is individually synchronized, usually by using start and stop bits.
2. Descriptive of the transmission method, or the terminal equipment employed, which demands timing information be included in the transmitted character.

Attenuation

The difference between transmitted and received power due to loss through equipment, lines, or other transmission devices.

Bandwidth

The difference between highest and lowest frequencies in a band, such as 3000 cycles bandwidth in a voice grade line (300-3,300 cycles).

Bit

 
1. An abbreviation of the words "binary digit."
2. A single character in a binary number.
3. A single pulse in a group of pulses.
4. A unit of information capacity of a storage device.

Carrier

A continuous frequency capable of being modulated with a second information-carrying signal.

Channel

A path for transmission of electromagnetic signals. Synonym for line and link. Compare with circuit.

Character

A member of a set of elements upon which agreement has been reached and that is used for the organization, control, or representation of data. Characters may be letters, digits, punctuation marks, or other sym bols.

Circuit

A means of two-way communication between two data terminal installation. Compare with the channel, line, and link.

Computer, Central

In data transmission, the computer that lies at the center of the network and generally does the basic centralized functions for which the network was designed. Synonym for host computer.

Data communications

 
1. The movement of encoded information by means of electrical transmission systems.
2. The transmission of data from one point to another.

Facilities

The elements of the telephone plant that provide a complete connection, exclusive of the customer's equipment.

front-end

An auxiliary processor that is placed between a computer central processing unit and transmission facilities. This device normally handles housekeeping functions such as management of line, translation of code s, etc.

Hardware

A generic, somewhat slang term used to include all equipment, both computer and communications, contained in a system.

Hertz (Hz)

Same as cycles per second; e.g., 3,000 Hertz is 3,000cycles per second.

Line

A channel or link.

Line, Leased (or private)

A line furnished to a subscriber for his exclusive use.

Line, Local Loop

A communication line connecting several terminals in the region of a single controller to that controller.

Message

A communication of information from a source to one or more destinations, usually in a code. A message is usually composed of three parts:

1. A heading, containing a suitable indicator of the beginning of the message together with some of the following information: source, destination, date, time, routing.
2. A body containing information to be communicated.
3.  An ending containing a suitable indicator of the end of the message.

A data communication operation in which messages are switched from one terminal location to another. Both lines must be free.

Modem

A contraction of the words "modulator-demodulator." A modem is a device for performing necessary signal transformation between terminal devices and communication lines. They are normally used in pairs, one at either e nd of the communication line.

Modulation

Alteration in the characteristic of a carrier signal by impressing an information signal on the carrier.

Modulation, Frequency

A form of modulation in which the frequency of the carrier is varied in accordance with the instantaneous value of modulating signal.

Modulation, Phase

A form of modulation in which the phase of the carrier is varied in accordance with the instantaneous value of modulating signal.

Network Control Program (NCP)

The program within the software system for a data processing system which deals with the control of the network.

Office

The common designation for any facility in the public switched network at which switching takes place.

Packet switching

The technique used when long messages are sub-divided into short packets where the maximum length is fixed.

Parallel

 
1. Pertaining to concurrent or simultaneous operation of two or more devices, or the concurrent performance of two or more activities in a single device.
2. Pertaining to concurrent simultaneous occurrence of two or more related activities in multiple devices or channels.
3. Pertaining to the simultaneous processing of the individual parts of a whole, such as bits of a character and characters of word using separate facilities with the various parts.

Phase

Pertaining to the relative timing of an alternating signal. Two signals may be identical in amplitude and frequency, but may differ in phase if one signal lags the other by any value not an exact multiple of the frequency.

Protocol

A procedure for synchronization so that the receiver knows when a bit starts and ends so that it can be sampled, similarly for character synchronization. The receiver can determine which bit belongs to a character, and similarly for message synchronization. The receiver can recognize a special character sequence that delineates messages.

Remote Job Entry (RJE)

Submission of jobs through an input unit that has access to a computer through data communication facilities.

Serial

 
1. Pertaining to the sequential performance of two or more activities in a single device.
2. Pertaining to the sequential or consecutive occurrence of two or more related activities in a single device or channel.
3. Pertaining to the sequential processing of the individual part of the whole, such as bits of a character, or the characters of a word using the same facilities for successive parts.

Software

A generic, somewhat slang term for a computer program, sometimes taken to include also documentation and procedures associated with such programs.

Start bit

A bit preceding the group of bits representing a character used to signal the arrival of the character in asynchronous transmission.

Station

One of the input or output points on a network.

Stop bit

 A bit used following the group of bits representing a character, to signal the end of a character in asynchronous transmission.

Store-and-forward

Applied to communication systems in which messages are received at intermediate points and stored.

Switched network

Any network in which switching is present and which is used to direct messages from the sender to the ultimate recipient.

System

A collection of people, machines, and methods organized to accomplish a set of specific functions.

System Network Architecture (SNA)

The term applied by IBM to conceptual framework used in defining data communication interaction with computer systems.

Teleprinter

A Teletype or Teletype device, consisting of a keyboard and a printing device.

Terminal, Video

A terminal using a video display as a readout device, in contradistinction to a teleprinter, which uses a printer device.

Transmission, Asynchronous

Transmission of data in which the entire messages does not operate from the same time base. Typically the bits that make up a single character are transmitted synchronously. However, there may be arbitrary delays b etween characters thus making the timing of characters truly asynchronous.

Trunk

A communication channels between switching devices or central offices.