公开(公告)号：US3588380A

公开(公告)日：1971-06-28

申请号：US3588380D

申请日：1969-03-21

Applicant: IBM

Inventor： HORLANDER FRANK J ,  YOUNT WILLIAM R

IPC: G09B5/06 ,  G11B5/02 ,  G11B5/86 ,  G11B25/04 ,  G11B5/44

CPC classification number: G11B25/04 ,  G09B5/062 ,  G11B5/02 ,  G11B5/865

Abstract: EDUCATIONAL APPARATUS IN THE FORM OF A RECORDING/REPRODUCING UNIT ACCOMMODATES A RECORD MEDIA COMPARABLE IN SIZE TO THE FAMILAR IBM TABULATION CARD. THE MEDIA HAS PRINTED INFORMATION ON ONE SIDE SUCH AS QUESTIONS AND ANSWERS, CIRCUIT DIAGRAMS, ETC. THAT IS VISIBLE TO THE USER WHEN IN OPERATING POSITION AND RECORDED INFORMATION ON THE OPPOSITE SIDE POSITIONED FOR SCANNING BY A TRANSDUCER DURING PLAYBACK AND RECORD MODES. ONE FEATURE OF THE MACHINE IS TO RECORD AND PLAYBACK SPEECH WHILE USING TWO DISTINCTLY DIFFERENT MAGNETIC RECORDING MATERIALS. THE FIRST MATERIAL (MASTER CARD) REPRESENTS THAT USED FOR THE DIRECT RECORDING OF MASTER RECORDS. IT IS OF HIGH COERCIVITY AND HIGH RETENTIVITY. THE SECOND MASTER (COPY CARD) HAS RELATIVELY LOWER MAG-

NETIC PROPERTIES. IN ORDER TO RECORD AND REPRODUCE WITH THE TWO DIFFERENT MATERIALS ON A COMMON RECORD/PLAYBACK MACHINE, THE CIRCUITS CONTROLLING THE HIGH FREQUENCY BIAS AND SIGNAL RECORDING CURRENTS ARE CHANGED DEPENDING IN THE TYPE OF MATERIAL USED. THIS IS ACCOMPLISHED BY ELECTRICAL SWITCHING OF EITHER OF TWO EQUALIZATION AS BIAS AND PREEMPHASIS NETWORKS IN THE RECORD CIRCUITS RELATED TO THE MASTER AND COPY MEDIA WHICH OCCURS AUTOMATICALLY WHENEVER THE RESPECTIVE MEDIA IS INSERTED. THE MASTER MEDIA IS INTENTIONALLY OVERRECORDED TO COMPENSATE FOR NOMINAL AND EXTREME SIGNAL LOSSES EXPECTED TO BE ENCOUNTERED WHEN THE MASTER MEDIA IS USED AS A SOURCE DURING A LATER MAGNETIC TRANSFER OPERATION.