Browse Prior Art Database

Public Data Network Communication From Text Processing Terminal Signal and Error Handling

IP.com Disclosure Number: IPCOM000045977D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 16K

Publishing Venue

IBM

Related People

Benignus, DM: AUTHOR [+4]

Abstract

In countries where Public Data Networks are available for communicatingdata between terminals, protocols have to be developed for accessing the Public Data Network and for effectively communicating between text processing terminals. The present approach provides for such communication, and particularly it provides an effective error-handling approach. The terminal will answer incoming calls and will allow the operator to place out-going calls or submit facility requests to the network.

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Public Data Network Communication From Text Processing Terminal Signal and Error Handling

In countries where Public Data Networks are available for communicatingdata between terminals, protocols have to be developed for accessing the Public Data Network and for effectively communicating between text processing terminals. The present approach provides for such communication, and particularly it provides an effective error-handling approach. The terminal will answer incoming calls and will allow the operator to place out- going calls or submit facility requests to the network.

When attached to a X.21 Public Data Network, the operator does not use a telephone to dial the remote station. After the CommunicationsStart key is pressed, information text is presented on the screen telling the operator whether or not the X.21 network is available. If the X.21 network is not available, the terminal will monitor the link and report when it becomes available. A prompt is then presented telling the operator to press the Call key to establish a connection.

The present X.21 network interface does not provide for retransmission when errors are detected in receive data during the call establishment phase. The two kinds of data that the terminal receives from the X.21 network are: calling and called station identification, and call progress signals. This information is presented to the operator, with explanatory text, on a summary display screen. If an error is detected in receiving a character, a substitute-code will be inserted in its place. The terminal prints and displays this substitute code as an underscore (_).

When a parity error is detected during call establishment, the terminal will insert a substitute code and will not present invalid data to the operator.

When attempting to establish a connection, the X.21 Public Data Network will return Call Progress Signals if a problem is detected by the X.21 network. Examples of these signals are: Number busy Called terminal powered off

In addition to the problems which are detected by the network, there are several problems which may be detected by the terminal. Examples of these problems are: Comparator errors on the terminal to network adapter Unable to transmit on the network

Informational messages will then appear on a session summary display screen on the terminal. These messages will keep the operator informed as to how the call is progressing. Optionally, these messages can be saved in the session summary to allow service personnel access to them.

Method

When the X.21 network becomes available (Ready), the following message will be logged: "Network Available"

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When the operator presses the Call key the following message appears: "Network Call/Request: yyyyyyy"

The network address or facility request presented to the network is shown as yyyyyyy.

The X.21 network provides call-status information to its user in the form of a two-digit Call Progress Signal. The Call Progress Signal...