The Phase-Shift Indicator is designed to measure the rotor phase angle of the Three-Phase Synchronous Motor/Generator, Model 8507. It consists of a transparent plastic disc, calibrated in electrical degrees, and a metal mounting bracket. It attaches to the end of the machine carriage with slide fasteners. The rotor phase angle can be read by illuminating the end of the machine shaft, through the calibrated disc, with a strobe light (the Stroboscope, Model 8922). The resulting value corresponds to the measured phase shift for a 4-pole ac machine, in electrical degrees.