The Shure A15PRS reverses the phase (polarity) of a balanced audio signal. Typical use applications include correcting polarity reversal caused by a wiring error in a microphone cable; connecting an unbalanced high impedance microphone having the "hot" signal on pin 3 to the input of a mixer that requires the "hot" signal on pin 2; and reducing phase cancellation/comb filtering between two signals that are of opposite polarity.

An in-line switch permits instant selection of either normal or reversed polarity for comparison purposes.