Rolling gates are generally operated with a mechanical drive system that utilizes wire rope drums such as the locks in Antwerp and the new Panama Canal locks. Wire rope drive systems are the most common type of drive for rolling gates and are recommended for new construction. The most common winch drive system and generally utilized for larger gates is two drums with wire rope reeling from the top (opening) and for closing from the bottom. This system also provides the most evenly distributed forces to the gate and is the recommended drive system. The gate is opened by synchronized movement of both cable drums whereby the top cables are pulling on the connection point of the gate. A cable tension control device, which is installed on every top cable, ensures that the bottom cable remains tight. An automatic wire rope tensioning system should be included in any new design. The Panama Canal and Kaiser Lock tension systems utilize a hydraulic cylinder. Although wire rope drives are the most common, there are other means to open and close rolling gates. This includes a chain system and a rack and pinion system. Chain drives are only incidentally utilized in rolling gate projects. The maintenance requirements of a chain system are generally greater than a wire rope drive system. Rack and pinion systems are also utilized to drive rolling gates including the new rolling gates at Ijmuiden Lock. The control system for a rolling gate is very similar to a movable bridge and shares many of the same features. A programmable logic controller (PLC) system is nearly always used today and recommended for all new construction. A back-up control system is also recommended such as a hard-wired system. The speed of the gate during movement is not constant. The gate speeds up gradually to the operating speed and it slowly decreases speed towards the end. This is intended to prevent high translatory waves in the gate chamber. It also limits the size of the machinery during the initial start-up and avoids oversizing machinery. The start-up loads are always higher due to inertial loads that need to be overcome. The control system has to be capable of varying and adjusting the gate speed.