Matrix Encoded 1V/Octave Keyboard
A keyboard is a central part of any synthesizer and this is a good keyboard circuit. It is monophonic in function i.e. its a single note keyboard. It performs the function of translating key presses into appropriate voltages so that you get 1V/Octave or .08333 volts per semitone. It also provides gate and trigger signals. The gate goes high when you press any key and remains high until all keys are released. The trigger emits a pulse (approximately 1 to 2 mS) each time a note is pressed or changed.
   Matrix Encoded 1V/Octave Keyboard
Full description at Matrix Encoded 1V/Octave Keyboard website
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