Pulse or digital communications – Spread spectrum – Direct sequence
Patent
1981-09-21
1984-04-17
Smith, Jerry
Pulse or digital communications
Spread spectrum
Direct sequence
375110, 360 44, 360 51, 360 40, 371 47, 364900, 364300, G08C 2500, G06F 300, H04L 700, G11B 506
Patent
active
044438834
ABSTRACT:
Data synchronization apparatus for a 1500 baud computer-audio frequency magnetic tape recorder interface is disclosed. The synchronization apparatus automatically detects bit cell boundaries and synchronizes at both the bit level and the byte level even if the audio waveform as read from the tape is inverted, as is the case with some tape recorders. Synchronization is performed by squaring the audio waveform and measuring two successive time intervals occurring between three successive positive-going transitions and subtracting the resulting measurements. If the calculated difference is less than a predetermined amount, positive-going transitions of the waveform are selected as bit cell boundaries. If, on the other hand, the calculated difference is greater than the predetermined amount, negative-going edges are selected as bit cell boundaries. Synchronization is achieved on a byte level by shifting incoming data into a first-in/first-out buffer and examining the stored data for a predetermined bit pattern.
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Niessen William G.
Smith Jerry
Tandy Corporation
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