3780 BSC/RJE Emulation Glossary

3780 BSC/RJE Communications Glossary


This glossary is a simplified overview of 3780 BSC/RJE emulation terminology directed toward non-technical readers. Where appropriate, embedded links have been included to take you outside the www.3780-emulation.com site to other resources for more detailed information.


201C - model number of 2400 bps synchronous modem manufactured by Bell Telephone and emulated by later designs from other manufacturers (i.e., Bell 201 compatible)

208B - model number of 4800 bps synchronous modem manufactured by Bell Telephone and emulated by later designs from other manufacturers (i.e., Bell 208 compatible)

2780 - model number of the original IBM bisync RJE data terminal

3770 - model number of a family of IBM SNA RJE data terminals

3780 - model number of the most commonly emulated IBM bisync RJE data terminal

API - acronym for Application Program Interface

Application Program Interface - a set software routines combined to create a development tool used to build application software (e.g. the BSCLIB Developer's Tool Kit) is 3780 RJE emulation API)

ASCII - acronym for American Standard Code for Information Interchange which is the character set used on most PCs (see translation)

async - abbreviation for asynchronous

asynchronous - a type of serial communications standard on virtually all PCs (i.e., via COM ports)

AutoSync - a feature built into Hayes Optima Business Modems that performs an asynchronous - synchronous conversion in real-time; AutoSync modems used with compatible software permit connection between synchronous and asynchronous devices without the need for a sync adapter (see sync adapter)

batch - set of one or more non-interactive commands submitted for processing

baud - a measure of line speed for data communications (see bps -- while not exactly the same, they are often used interchangeably)

Binary Synchronous Communications - a byte-oriented, blocked, error-correcting data communications protocol invented by IBM in the 1960s

bisync - abbreviation for Binary Synchronous Communications

bps - acronym for bits per second which is a measure of data communications speed (see baud -- while not exactly the same, they are often used interchangeably)

BSC - acronym for Binary Synchronous Communications (see bisync)

BTAM - acronym for Basic Telecommunications Access Method, a communications sub-system on IBM mainframes; a predecessor to VTAM

constant carrier - a term meaningful in conjunction with full-duplex modem communications indicating the absence of line turnaround delays (all modern V.32, V.34, and V.90 modems support constant carrier operation)

contention mode - a term that is used when describing which device sends and which receives in a point-to-point bisync connection

control unit - see front end controller

controlling station - the central device in a multi-point environment; may also be called a control station

dial-up - a term applied to data communication connections over normal, switched telephone lines (see POTS, switched line)

duplex - see half-duplex, full-duplex

EBCDIC - acronym for Extended Binary Coded Decimal Interchange Code which is the character set used on must mainframe computers (see translation)

EDI - acronym for Electronic Data Interchange

Electronic Data Interchange - a widely accepted method of transmitting and receiving business related documents, such as purchase orders and bills of lading, electronically

emulation - when one device imitates or appears to be another device

FEP - acronym for Front End Processor (see front end controller)

FRAD - acronym for Frame Relay Access Device or Frame Relay Assembler/Disassembler

Frame Relay Access Device - a device for accessing a Frame Relay network

front end controller - a term applied to a data communications sub-processor (or control unit) on IBM mainframe computers to which remote terminals are often attached; Model 3745 is the most commonly installed front end controller on IBM mainframes (also referred as a "front end processor" or FEP)

full-duplex - a communications method where data can be sent in two directions simultaneously

half-duplex - a communications method where data is only sent in one direction at a time (bisync is a half-duplex protocol)

JCL - acronym for Job Control Language (a set of commands to manage submission of RJE jobs to an IBM mainframe)

JES - acronym for Job Entry System (an RJE subsystem on IBM mainframes)

job - in legacy systems most processing was not interactive but consisted of batch processing jobs; in RJE sessions, the files sent from a terminal to the mainframe are still seen as a job; a job consists of commands (called JCL) for the mainframe (e.g., to run a particular program) and optionally data to be used as input to the program

Job Control Language - a set of commands for IBM mainframe computers to control the execution of programs and the submission of data from remote job entry (RJE) terminals

leased line - a dedicated point-to-point telephone connection as opposed to dial-up or switched lines

legacy system - a term in use today when referring to entrenched computer systems that were installed years ago that are typically too costly to replace; this term is most often used when referring to mainframe computer systems

legacy system integration - a term used to describe the happy blending of legacy systems with modern day PC and Internet technology

line turnaround - an action where one side of a communications session stops transmitting and "turns the line around" to receive (or vice versa); there is usually a delay while this action takes place (i.e., line turnaround delay); this is a condition specific to half-duplex, switched carrier connections

master station - may be used when referring to the primary station in a point-to-point bisync environment or the controlling station in a multi-point bisync environment

modem - acronym for modulator-demodulator which is an analog device for the transmission of data over telephone lines

multi-point - a data communications connection between two or more devices where there is typically a single controlling station and one or more satellite (or tributary) stations

MVS - acronym for Multiple Virtual Systems, an IBM mainframe operating system

peer-to-peer - a data communications connection where all parties in the connection have the same capabilities

point-to-point - a data communications connection between only two devices

poll - a term applied to the action of the controlling station in a multi-point environment requesting if tributary station(s) have anything to send

POTS - acronym for the telephone network which stands for Plain Old Telephone Service

primary station - the device in a point-to-point connection with higher priority designed to avoid contention problems (see contention mode, secondary station)

printer - name of the primary output device of an RJE terminal (corresponded to the physical printer in the 3780 terminal)

protocol - a defined method of exchanging data between devices

punch - name of the secondary output device of an RJE terminal (corresponded to the physical card punch in the 3780 terminal)

reader - name of the input device of an RJE terminal (corresponded to the physical punched card reader in the 3780 terminal)

remote job entry - a method for submitting batch computer programs that originated in the days of punched cards

RJE - acronym for Remote Job Entry

SDLC - acronym for Synchronous Data Link Control which is a bit-oriented, error-correcting communications protocol invented by IBM for use in conjunction with SNA as a successor to bisync

secondary station - the device in a point-to-point connection with lower priority designed to avoid contention problems (see contention mode, primary station)

select - a term applied to the action of the controlling station in a multi-point environment to send data to tributary station(s)

session - a term often used when describing connecting one or more computers, exchanging data, and disconnecting (i.e., a communications session)

slave station - see secondary station, tributary station

SNA - acronym for Systems Network Architecture, a large scale networking protocol invented by IBM

switched carrier - a term meaningful in conjunction with half-duplex modem communications where line turnaround delays were unavoidable (older Bell 201 and 208 modems supported only switched carrier operation)

switched line - a term applied to dial-up telephone line to which a modem is attached

sync - a abbreviation for synchronous

sync adapter - an adapter card that provides one or more synchronous communications ports to a PC; the COM ports in PCs only support asynchronous communications so the addition of an adapter is often required to connect a PC to a mainframe (for an exception, see AutoSync)

synchronous - a type of serial communications typically used in mainframe connectivity

TCAM - acronym for Tele-Communications Access Method, a communications sub-system for IBM mainframes; a predecessor to BTAM

translation - in the RJE world, this typically is referring to ASCII - EBCDIC translation performed by an emulator; ASCII is the native character set on PCs while EBCDIC is the native character set on a great many mainframe systems; effective translation between these different character sets is essential for meaningful data transmissions between the two

tributary station - a subordinate device in a multi-point environment (see poll, select)

unswitched line - see leased line

V.32 - a term used to generally classify 14.4K bps modems

V.34 - a term used to generally classify 33.6K bps modems

V.90 - a term used to generally classify 56K bps modems

VM - acronym for Virtual Machine, an IBM mainframe operating system

VTAM - acronym for Virtual Telecommunications Access Method, a communications sub-system for IBM mainframes; successor to BTAM and TCAM
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