This document discusses hydraulic circuits and systems used in industry. It covers accumulators, intensifiers, and various hydraulic circuits like regenerative circuits, pump unloading circuits, and circuits for pressure intensification, air-over-oil, sequencing, reciprocation, synchronization, fail-safe operations, speed control, and deceleration. It also discusses sizing hydraulic systems, hydrostatic transmission, electrohydraulic circuits, servo and proportional valves, and their applications in mechanical and hydraulic servo systems.