Abstract: Apparatus (FIG. 1), for training in the rapid and accurate reaction to a situation confronting one or more trainees 12, 12' in an enclosed room 11, has one wall thereof formed by a screen portion 14 onto which an optical image is back-projected by projector 16. Each trainee's weapon 22 has a light emitter 24 responsive to firing the gun (containing blanks) at the screen to simulate the projectile impact point by spot 26. A television camera adjacent the projector and viewing the rear of the screen receives the spot and relates the position of this within the camera field to datum points of the projected image, the datum points 36' being visible to the camera and not the trainee.

Abstract: A marine mine 10 (FIG. 4) is arranged to have a buoyancy state in which the force of gravity and/or buoyancy act on the mine in a vertical direction to move the mine through the water and includes control means operable to control guidance surfaces 16, 17, 18 projecting from the mine to impart a lateral gliding movement to the mine to steer it to intercept a target. The buoyancy state is determined by a buoyancy compartment forming part of the mine body which may be flooded to lay the mine at a submerged station. Sonar sensing means detecting a target causes air from a cartridge to displace water from the buoyancy compartment to provide an upward buoyancy force which is used to give lateral movement to the mine which is steered on a trajectory intercepting the target.