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Method of Recovering from Loss of End Of Block Character in a Communications System

IP.com Disclosure Number: IPCOM000090505D
Original Publication Date: 1969-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Harbour, WP: AUTHOR [+2]

Abstract

A communication system repeats the transmission of end-of-block and check characters when no answer-back is received from the receiving terminal to indicate that the previous transmission of data is or is not correctly received. Therefore, when an end-of-block character itself is perturbated on line, so that the receiver does not recognize it as such, the system does not lock up. The repeat of the end-of-block and block check characters by the transmitter, after an appropriate time when no answer is received, prompts an error response by the receiving terminal so that the transmitter knows to repeat the previous block of data and then to continue with the transmission.

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Method of Recovering from Loss of End Of Block Character in a Communications System

A communication system repeats the transmission of end-of-block and check characters when no answer-back is received from the receiving terminal to indicate that the previous transmission of data is or is not correctly received. Therefore, when an end-of-block character itself is perturbated on line, so that the receiver does not recognize it as such, the system does not lock up. The repeat of the end-of-block and block check characters by the transmitter, after an appropriate time when no answer is received, prompts an error response by the receiving terminal so that the transmitter knows to repeat the previous block of data and then to continue with the transmission.

In a communication system, the possibility that a character can be lost or changed on line always exists. Error detection is usually accomplished by both transmitter and receiver generating check characters from the information transmitted and received respectively. Check characters are functions of the data transmitted and received and are generated by both the transmitter and the receiver. After completion of the transmission of the information, the transmitter sends an end-of-block character to inform the receiver that the next character is the check character which is generated by the transmitter.

The receiver also generates a check character from the data it receives. When it receives the check characters, it compares them with those it generates. If the check characters received are the same as those generated internally, it is assumed that the information is correctly received and the receiver sends a positive answer. If they do not compare, then the receiver assumes that the block is received incorrectly and informs the transmitter that the information is not correctly received. In this case, the transmitter repeats the transmission of the information.

Sometimes the end-of-block character its...