Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1982-07-15
1985-07-16
Caldwell, Sr., John W.
Communications: electrical
Audible indication
Percussion-type sound producer
340365E, 340365S, 178 17C, 4004792, G08C 900
Patent
active
045299676
ABSTRACT:
An inductive keyboard, including, printed circuit patterns forming a multiplicity of key excitation patterns and key sensing patterns. The key excitation patterns are divided into groups of excitation patterns formed in rows. The key sensing patterns are divided into groups of sensing patterns formed in columns. Each key excitation pattern has an adjacent complementary key sensing pattern for providing output signals from the sensing patterns in different columns by passing an excitation signal through an individual row of excitation patterns. At least one movable element is located adjacent each pair of complementary key excitation and sensing patterns. The movement of each movable element is between positions close to and away from each pair of complementary patterns to provide for a change in the output signal from the individual key sensing patterns. Printed circuit reference patterns form at least one excitation reference pattern and one sensing reference pattern. The excitation reference pattern are coupled to the excitation key patterns to have the excitation signal pass through the reference excitation pattern for providing at least one reference signal from the sensing reference pattern. One or more comparators provide a comparison between the reference signal and the output signals to provide a comparison of the modulated mutual inductance of the key patterns with the mutual inductance of the reference patterns independently of the excitation current.
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Caldwell Sr. John W.
Heim Michael F.
Roston Ellsworth R.
Schwartz Charles H.
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