A frequency-modulated RADIUS is projected onto a target. The target returns this RADIUS to the device. Laser rangefinder Principle of operation A frequency-modulated RADIUS is projected onto a target. The target returns this RADIUS to the device. The time taken by the Department to return is measured and the distance between the user of the target is calculated. A neighbour principle is used by security forces to carry out speed checks. The speedometer is implementing the infrared radiation emitted by a laser pulse trains. When the beam encounters a target in motion (vehicle), a fraction of the beam is returned to the speedometer (reflective beam). The measurement of the speed of the targeted vehicles is determined from the change in the interval between the pulses reflected by the vehicle. The vehicle moves away quickly, more time separating two successive reflected pulses increases (Doppler effect)\ [archive] In the armed forces Technology has allowed to develop systems to aid in the conduct of shooting with the development of laser rangefinder coupled to a ballistic computer whose purpose is to calculate the correction to apply to the angle and direction of the barrel depending on the distance , the direction and speed of the purpose, to the type of ammunition present in the cylinder head as a gun can fire several types of shells, speed and the direction of the tank shooter, the speed and the direction of the wind, etc. Simply send a signature laser on the target and shoot. With this principle, we know the distance of the shot in the goal. Simply renew the process after a time given t and calculate the difference in the two time α1 and α2. The result is a time v which is nothing other than the time image of the distance travelled during a time given t. With deducted information from the simple calculation of the distance from the time, we get the speed.