A retractable turret as a technical piece of equipment; it can turn 360 degrees and move up and down. It has the fire power of field battery with 8 canons. Retractable turret were already in service in the forts in 1914. The roof of the retractable turret is 30 cm thick. Because of the small size the retractable turret is a difficult target. The turret has three levels

On the Ground floor: is a balance arm with and a 18 ton contra weight; with an electric motor the turret is moved up and down. In case of power failure two men can move the turret .

On the middle floor: is the control panel. Here the grenades are loaded for the top floor and the turret and canons are directed into it's fire position. All systems are working electric

On the top floor: are the two 75 mm canons and two me loading the grandees.

There are different types of retractable turret:

• for two 135 mm heavy mortar
• for two 81 mm mortar
• for two 75 mm canon
• for two 7,5 mm heavy machine gun
• for four 7,5 heavy machine guns with two 25 mm anti-tank guns.