The SLC, nicknamed “maiale” (pig), was a slow-speed torpedo manned by two operators equipped with autonomous underwater breathing apparatus  and an explosive charge to be placed under the enemy ship’s.

Designed on the eve of WWII after the old T.S.R. limpet mines, the first SLCs  were 7.30 m long; they were propelled by a 1.6 HP electric motor, powered by a storage battery. They could reach a maximum speed of 3 knots and had a range of about 15 miles at a speed of 2.5 knots.

The human torpedo consisted of three sections. The first head round section contained the explosive charge (about 230 kg of Tritolital) and relevant explosive device. This element could be removed and placed under the ship’s keel. The central round part hosted the batteries and two seats for the operators. The third section, called “tail”, housed the motor and the equipment including rudders and propellers. A magnetic compass,  a depth gauge, a watch, two ammeters and a spirit level completed the instrumentation.