Browse Prior Art Database

Block Return Synchronization for Communication Terminals

IP.com Disclosure Number: IPCOM000093100D
Original Publication Date: 1967-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 3 page(s) / 53K

Publishing Venue

IBM

Related People

Harbour, WP: AUTHOR [+3]

Abstract

This is an error backup synchronization device for a magnetic tape transmitter and receiver. Both the transmitter and receiver back up to the start of a record block for retransmission of that record block when it is received in error.

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Block Return Synchronization for Communication Terminals

This is an error backup synchronization device for a magnetic tape transmitter and receiver. Both the transmitter and receiver back up to the start of a record block for retransmission of that record block when it is received in error.

Transmitting station 1 1 transmits information, previously recorded on magnetic tape 13, to receiving station 15 where the information is recorded on magnetic tape 17. Information can be recorded on tape 13 in varying formats. One format utilized is to record a start transmission character 18 followed by a block of data information 19, an end-of-transmission character 20, a check character 21, and an acknowledgement character 22 which is sent from the receiver. The characters other than data 19 need not be recorded since they are generated by the terminal. In operation, tape 13 is driven from left to right past read-record head 23 by incremental drive 25 a character at a time. Head 23 senses each character recorded on tape 13 serially-by-character and parallel-by- bit. The character so sensed is sent to single character buffer 27. Then it is sent serially-by-bit, serially-by-character by communication channel 29 to station 15. When a complete character is sent, empty detect circuit 31 gates clock 33. The latter causes drive 25 to advance one character increment and causes the character read during that advance to be sent to buffer 27.

Data bits are received serially from communication channel 29 at receiver 15 and are stored in buffer 35. This occurs until full detect circuit 37 detects the presence of a complete character. Detect 37 gates clock 39. This causes the character located in buffer 35 to be recorded by head 41 on tape 17 and causes drive 43 to advance tape 17 one character position past head 41.

At the completion of transmission of data 19, end-of-block character 20 is sent to station 15 which signals that the message is complete. Check character 21 is then sent which is compared with checking information generated by checking circuit 45. If check character 21 agrees with the checking information generated at station 15, circuit 45 causes an affirmative response to be sent to buffer 35 for transmission to station 11. If the two signals compare unfa...