Plus2Minus

This circuit is for converting a positive-triggered contact in a pipe organ console to output a negative signal for MIDI encoding.

Jay Riedl

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Description

In my 1953 United organ console, the Peterson electronic combination action requires that the stops, couplers, and pistons maintain a 12 volt DC positive trigger. The MIDI encoding electronics require a negative trigger. This circuit will convert the positive trigger to a negative trigger via ground. The quick switching and recovery time Toshiba TLP-222A photocouplers allow this interface to be ideal in a musical instrument.