Detector for disc records
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United States of America Patent
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-
Apr 3, 1990
Grant Date -
N/A
app pub date -
Feb 10, 1989
filing date -
Mar 2, 1988
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A record detector includes a member having a capacitance that changes in response to capacitive coupling with a metallic layer of the record. The variable capacitance member controls an electrical oscillator that produces an electrical signal having a frequency that varies in response to the value of the capacitance. Changes in the frequency of the electrical signal are measured in analog or digital form. The magnitude of the frequency change is compared to one or more reference values to determine whether an optical disc record is present and to determine other characteristics, such as size and orientation, of an optical disc record. The variable capacitance member is constructed by applying one or more metallic plates to an optical disc record support, or to the periphery of an optical disc record insertion slot, that is part of an optical disc record playback unit.
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