(5) Operation and maintenance of marine radio equipment. (6) Operation of radio direction finder. [Illustration: _Figure 45. Outboard profile showing cathead and cargo booms._] [Illustration: _Figure 46. Forty-ton cathead mounted on bow of ship._] =h. Gyrocompass instruction.= The Navy gyrocompass school teaches: (1) Basic principles of the action and operation of the gyrocompass. (2) Cause of gyrocompass errors and how to correct or compensate them. (3) Maintenance and care of the compass and its equipment. =i. Convoy communication.= The Navy convoy communication school teaches the various types of signaling used between ships in a convoy. The instruction includes: (1) Naval signal codes and calls. (2) Procedure signs. =j. Machine-shop training.= The machine-shop training includes the operation of drill presses, grinders, lathes, cutters, punch and shear machines, shapers, forging hammers, and milling machines. The men work with different types of metals, receive practical experience in various kinds of machine-shop jobs, and learn how to maintain the equipment and tools. =k. Demolition training.= Training in explosives and demolitions includes the following: (1) Theory of explosives. (2) Calculation of charges. (3) Capping and priming. (4) Field expedients. (5) Cutting, cratering, and flattening charges. (6) Booby traps. 13. SHIPBOARD TRAINING. Training aboard ship involves molding the crew into an efficient, smooth-running organization. This requires constant drill, practice, and working out of operational team problems. [Illustration: _Figure 47. Single-speed winch for operating 10-ton cargo boom._] [Illustration: _Figure 48. Fifty-ton barge made up of 21 sections and propelled by 115-hp outboard engine._] SECTION V OPERATIONS 14. CONDITIONS OF CAPTURED PORTS. =a. General.= Enemy destruction of a port’s facilities generally may be divided into two classifications. (1) _Channels and harbors._ Offshore obstructions in the waters of the harbor include booms and torpedo nets, debris, prepared sunken obstacles, destruction of navigation aids and moorings, and damage to underwater pilings and foundations. It is the engineer port repair ship’s job to remove or destroy these obstacles and to make the underwater repairs. (2) _Damage to shore installations._ The destruction of shore installations includes damage to utilities, shops, warehouses, railway spurs and yards, roads, bridges, locked basins, cargo-handling equipment, piers, wharves, and quays. It is the mission of the port construction and repair groups to repair and put these facilities back in operation. [Illustration: _Figure 49. Naples harbor cluttered with wreckage. Wrecked and capsized merchant vessels line the quays. Note the damaged warehouses. All cargo-handling equipment has been destroyed._] =b. Enemy damage to captured ports.= Although the conditions outlined below will not hold true in all cases, they were found in captured ports.