公开(公告)号：US3619569A

公开(公告)日：1971-11-09

申请号：US3619569D

申请日：1970-07-15

申请人： RCA CORP

发明人： HOEHN JACOB GEORGE ,  MANCINI RONALD ALFRED

IPC分类号： G06K5/00 ,  G06K7/016 ,  G06K7/10 ,  G01N21/48 ,  G06K9/02

CPC分类号： G06K7/10851 ,  G06K5/00 ,  G06K7/0163

摘要： A mark sense card reader employs dual-threshold circuitry to indicate the presence, absence or inability to determine the presence or absence of marks such as pencil marks on a card. The circuitry includes a light-sensing transducer coupled to first and second differential amplifiers. The first such amplifier produces an indication only when a mark is definitely present. The second such amplifier produces an indication both when a mark is present and when the light level is such that no decision can be made as to whether or not a mark is present. The presence of this last indication concurrently with the absence of the other such indication means that no decision can be reached as to whether or not a mark is present. This situation may occur in cases of a poor erasure, or very light marks and in such cases the circuitry of the present disclosure causes the card to be rejected.