3612835 is referenced by 165 patents and cites 2 patents.

A combined optical and magnetic transducer for sensing both optical and magnetic properties of an article, for example, a piece of paper currency or other document having both visible and magnetic markings to be tested or read, an information-bearing medium such as a data-recording tape to be read, or the like. The transducer comprises a magnetic-sensing head having a transparent gap separating the poles of the magnetic core of the head, a photoelectric element being disposed in the head in alignment with the gap. Outside the head, one side of the article contacts or is in close proximity to the poles at the gap, and the article is illuminated by a light source, so that both magnetic properties and optical properties of the article may be detected simultaneously during relative movement of the article and the transducer.

Title
Combined optical and magnetic transducer
Application Number
04/886,530
Publication Number
3612835
Application Date
December 19, 1969
Publication Date
October 12, 1971
Inventor
Ptacek James F
Andrews Boley A
Assignee
The Vendo Company
IPC
G06k 07/01
G11B 13/00
G07D 07/12
G07D 07/00
G06K 07/00
G11B 13/04
G07D 07/04
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