GB1369656A - Signal selecting systems - Google Patents

Abstract

1369656 Electrophoric musical instruments MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 12 Nov 1971 [29 Nov 1970] 52600/71 Heading G5J A signal selecting system for a keyboard type electronic instrument comprises a plurality of tone signal sources 1-4, a plurality of gate means for controlling the feeding of said sources to amplifier 104, the gates being controlled by a plurality of memory means 21-24 associated with a plurality of switches 11-14. Each memory responds to the operation of a corresponding switch to assume a first or second condition in which it respectively opens and closes the associated gate 31-34. The tone signal soruces 1-4 are arranged in frequencies corresponding to a rising musical scale, and if, on closing switch 12 to a gate (32, say), reset means 42 is provided such that, if any memory corresponding to a frequency higher than 22, is holding its gate open, that memory will receive a reset pulse from reset means 42 via' diodes 53 ..., thereby returning said memory to first condition and closing the corresponding gate. This ensures that on simultaneous closing of more than one switch 11-14, only the tone source of lowest frequency will be fed to the amplifier 104. Diodes 51, 52 ... 53 prevent the reset signal reaching memories operating on signals of lower frequency. Further, the common reset means 101 detects a condition where two or more memory means are set in the second condition, by comparing the output D.C. potentials with a reference potential and resets any memory previously set. Memory means 21-24 may comprise a flip-flop circuit (not shown) or a cascade transistor switch circuit (not shown). Reset means 41-43 may comprise an electrical conductor, an isolating resistor or diode. Each gate means 31-34 comprises two resistors in series between generator 1-4 and amplifier 104. Actuation of each gate is controlled by the impedance of the memory output preserved at the junction of the resistors.