Throttle Position Sensor Most (TPI) throttle position indicator sensors have extra pins for extra functionality, but for this discussion the three wire design will be discussed. To help explain this, these three leads and their function as it relates to engine and transmission performance are analyzed.
In music, the tonic is the first scale degree of a diatonic scale and the tonal center or final resolution tone. The triad formed on the tonic note, the tonic chord, is thus the most significant chord. More generally, the tonic is the pitch upon which all other pitches of a piece are hierarchically referenced. Scales are named after their tonics, thus the tonic of the scale of C is the note C.
In music, the subdominant is the technical name for the fourth tonal degree of the diatonic scale. It is so called because it is the same distance  below  the tonic as the dominant is above the tonic-in other words, the tonic is the dominant of the subdominant. It also happens to be the note immediately below the dominant. It is sung as fa in solfege.