The various ports and internal channels in these blocks help with easier controlling of the complex hydraulic or pneumatic behavior of the system. The control of the seven main functions of drilling top drives is a highlighted example of such systems which is operated through hydraulic manifolds characterized by a very complex structure due to both the limited space and high performance. The noted seven drilling functions include brakes, closing the Inside Blowout Preventer (IBOP) in case of emergency, closing the pipe, etc. Hydraulic manifolds convert the electrical messages received from the control room to the hydraulic commands that can be transferred to the functions. Meanwhile, the main hydraulic manifold of Varco top drive (USA), as the main hydraulic controller system of drilling operations, has much more complexities than other types of drilling top drives. Fortunately, the technical knowledge for such devise is acquired by ASA Company through a systematic research and development process. The result has been successfully approved after passing the field tests. This controller features 280 internal channels, 23 safety and control valves and 134 connections and test ports, and works with a hydraulic pressure of about 3000 psi.