Communications: electrical – Audible indication – Percussion-type sound producer
Patent
1981-01-28
1985-01-15
Groody, James J.
Communications: electrical
Audible indication
Percussion-type sound producer
336110, 336130, 340365R, 340365S, 4004792, G06F 302
Patent
active
044941099
ABSTRACT:
Noncontacting transformer switches are interconnected into keyboard networks which include insertable magnetic core, shorted turn or combination actuators. In a preferred embodiment, windings are provided and interconnected to form differential transformers. An actuator is inserted through one primary/secondary winding pair to switch the differential transformer between a balanced or "off" state and an unbalanced or "on" state. In one embodiment, single turn primary windings and their interconnecting network are printed on one side of a printed circuit board, and single turn secondary windings and their interconnecting network are printed in proper alignment on the opposite side of the board. A single hole aligned with a switched primary/secondary winding pair is provided for each transformer switch and actuators are arranged to be inserted through the holes. The transformer switches may be arranged to form a matrix array with the secondary windings connected to form a plurality of series connected winding rows and the primary windings connected to form a plurality of series connected winding columns. The printed wiring can be reduced for a given switch array by combining all nonswitched primary/secondary winding pairs into a single row of pairs which are differentially interconnected to the remaining rows of switched pairs. Keyboard touch control is provided by selectable amplifier driver power and threshold levels of comparators in keyboard scanner circuitry.
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