The Doble F2253 Power System Simulator performs integrity and application tests on complete protection schemes and individual relays. Run Steady-State, Dynamic-State and optional Transient Simulation tests with the F2253. The evolutionary design of the F2253 Simulator is based on the in-service experience of over five thousand F2000 instruments and dramatically improves protection maintenance productivity. The F2253 Simulator and ProTest software are revolutionary solutions which improve productivity of all protection maintenance. The F2253 reproduces phasor and logic signals and verifies protection scheme response. Scheme diagnostics are more effective than steady-state calibration tests because they evaluate the integrated response of the complete protection scheme to actual power system disturbance conditions, verifying performance under in-service conditions.