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RJE Terminal Overview

Both bisync and SNA/SDLC Remote Job Entry (RJE) terminals operate in the same manner; they collect information off-line and then transmit the data in large blocks to the host. Over the years, many different bisync and SNA RJE terminals have been introduced. The major terminals are:
    Bisync SNA/SDLC
    2770
    2780
    3741
    3780    		 3770 SLU
    3777 MLU
    LU 0

To facilitate the transfer of data, the terminals use special features to reduce the amount of data sent through the communications line. Various terminals support different subsets of the available features. The features include:
Space Compression The transmitting bisync or SNA/SDLC terminal replaces consecutive strings of spaces with a counter of the number of spaces. The receiving device restores the spaces.
Character Compression The transmitting SNA terminal replaces consecutive strings of the same character with a counter. The receiving device restores the characters.
Character Compaction The transmitting SNA terminal uses a host supplied compaction table to replace characters with a HEX code. The receiving device uses the table to restore the characters.
Printer Commands All RJE stations use special commands to format the data stream for the printer. Bisync terminals use a Carriage Control Tape (or forms buffer) to control paper movement. The tape designates channels which indicate a number of lines. The application instructs the printer to skip to a channel, thereby saving new line commands. SNA terminals use SCS (SNA Character String) commands to format the printer output.
ID Sequence RJE terminals use dial modems to connect to the host. Bisync terminals can use an ID sequence to verify that the proper terminal is communicating with the host application. SNA terminals use an Exchange ID (XID) to perform the same function.
Component Selection The bisync host application can use component selection to route data to a specific peripheral device (for example: card punch). An SNA/SDLC host application assigns each peripheral device a separate logical unit address. An SNA/SDLC terminal with more than one LU address is a Multiple Logical Unit (MLU) station.

To view the available options that can be specified for these protocols, select the appropriate protocol from the worksheets. If you have any questions, please e-mail us.