Abstract: An identification friend-or-foe system for vehicles wherein each vehicle is provided with a radiation transmitter and a receiver with a detector for detecting radiation transmitted by other vehicles. Each transmitter can transmit a first coded signal which can be detected by the receivers in other vehicles, the receivers providing an unblocking signal after the first coded signal is correctly identified. The unblocking signal clears a radiation transmission path in the vehicle, the path containing a reflector which reflects the received signal back to the source of the transmission. The reflector adds a further predetermined code to the signal reflected from the reflector with each vehicle having another detector for detecting a reflected signal and a device to identify the further predetermined code.

Abstract: The thermal deformation of an edge-restrained plate is expressed as a deflection of the plate out of its plane. Where the plate is used as a reference plane, the deformation of the plate can be quantitatively monitored and compensated for. In the case of a radiantly heated plate, the temperature gradient adjacent an edge of the plate is a linear function of the plate deformation. With convective cooling, the temperature drop from an initial condition relates linearly to deformation. Consequently, relatively simple temperature measurements will provide the necessary information. The invention has particular application to the roof of a military tank turret that is used as a reference plane for a gun sighting system.

Abstract: A muzzle reference system is provided for correcting errors in aiming signals produced by a fire-control system of an artillery gun having a gun muzzle pivotable about a first axis and movable about a second axis extending perpendicularly of the first axis. A laser beam transmitting unit adapted to be mounted on the gun for movement with the barrel about the second axis, directs a laser beam along an optical axis in response to an activating signal. A reflection unit, adapted to be mounted at the distal end of the barrel, reflects a laser beam received from the transmitting unit along the optical axis substantially along a reference optical axis at a predetermined angular position of the barrel about the first axis. A laser beam receiving unit, adapted to be mounted on the gun, receives a laser beam reflected substantially along the reference optical axis and produces signals representative of the deviation of the reflected beam from the perdetermined optical axis.