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Data Sampling Method

IP.com Disclosure Number: IPCOM000097242D
Original Publication Date: 1962-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 3 page(s) / 34K

Publishing Venue

IBM

Related People

Stahl, WL: AUTHOR

Abstract

In data transmission over long lines, various arrangements are used to adjust the time of occurrence of data sampling pulses at a receiver to maintain the sample pulse in the center of received mark and space signals. One system uses a frequency divider for generating the sample pulse. In this, the deviation from the center of signals is corrected by either advancing or retarding the output of the divider by a predetermined number of input pulses.

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Data Sampling Method

In data transmission over long lines, various arrangements are used to adjust the time of occurrence of data sampling pulses at a receiver to maintain the sample pulse in the center of received mark and space signals. One system uses a frequency divider for generating the sample pulse. In this, the deviation from the center of signals is corrected by either advancing or retarding the output of the divider by a predetermined number of input pulses.

In cryptographic data transmission it becomes necessary that, after an intermittent break in transmission, the receiver be able to place the sample pulses in the center of precisely related, received signals. For example, if the receiving oscillator drifts during a line break so that the nth sample pulse from the start of a message does not coincide with the nth signal of the message, the receiver is never able to accumulate the proper combination of signals to produce a valid character. This is because the centering arrangement is unable to adjust the sample pulse more than one signal. It is only capable of centering the pulse within a particular signal period.

The difficulty is remedied by assuming the requirement for correction before a linebreak continues during the break and by proceeding in accordance with the following steps: 1. When the line breaks, remember the last correction made, whether advance or retard. 2. When the line is re-established, attempt to recognize a valid character. 3. If a valid character is recognized, resume normal sample pulse centering procedure....