The High Pressure (H.P.) cutout is a protective relay in refrigeration and air conditioning systems. It prevents compressor damage by stopping operation when discharge pressure exceeds safe limits. The H.P. cutout opens the circuit automatically when discharge line pressure becomes too high, safeguarding the compressor and other components from excessive pressure damage. Conversely, the L.P. cutout responds to low suction pressure, not discharge pressure. A relay is a general switch, and an overload protector addresses electrical overload, not pressure issues.