 This is the site of the Ground Surveillance Radar ANTPS-25. In a previous film, this radar was shown to be a transportable set, intended to detect, locate and identify moving ground targets. The set will supplement the artillery forward observers' surveillance of the battlefield during periods of reduced visibility or night hours. This film will be devoted to audio returns from various types of moving targets. For purposes of instruction, it is assumed the radar section has been ordered to observe the approaches to six key points in the area of interest. Each key point is assigned a concentration number. Concentration Alpha Alpha 101, Alpha Alpha 102, Alpha Alpha 103, Alpha Alpha 104, Alpha Alpha 105, Alpha Alpha 106. Each area is observed for a short period. The areas are small, but there are six of them to monitor. If nothing is detected at any one point, the surveillance is moved to the next point in turn. The radar will be operated in Mode 5 throughout the film. In this mode, audio target returns will be received only from an area 36 miles wide and 75 meters long, giving the accuracy required for effective locations of enemy moving targets. The first of the key points for observation, concentration Alpha Alpha 101. The map indicates a small road running through partial cover. Here the sound coming from the radar's loudspeaker. It is the unique feature of this radar, an electronic return echo created by the radar based on the Doppler effect. By the sound alone, trained operators identify the nature of a moving target. Let's go out and take a look at this Alpha Alpha 101 terrain. See the lay of the land. See just what could be expected from the topographical markings on the map. A clearing between woods, a small road, but nothing moving. No men, no machines. Then what caused that audio return of the radar loudspeaker? Fixed terrain features such as vegetation can act like a moving target. Branches of trees, tall grass. Learn to identify this sound as nearly background noise. Except in the case of moving men, background noise is rarely interfere with target identification. Let's see how a radar operator handles this approach point. Still no audio return from a moving target. Only the background noise from fixed but moving terrain features. But now listen to this. The audio return from a moving target. From the sound alone, the trained operator recognizes the target. He does not need to be at the actual country road. But we do, to know that this sound is caused by this target. For the radar operator, an electronic sound took the place of sight. For each type of moving target, the ANTPS-25 radar creates a characteristic and unmistakable return echo. In fact, an electronic signature. Learn to know audio return sounds by heart. When heard, the mind's eye should see the moving target just as it is seen here. Radar operators follow a set routine. Target detected. Audio return identified. Location and nature of target reported. The report goes in. Nature of target. How many? What doing? Location. After reporting a target, no time is lost in moving the radar beam on to the next area concentration for surveillance. From here to here. Topographical markings indicate a different kind of road in flat terrain. Here's the road. Nothing moves under the night skies. Operators at the far off radar are not misled by calm and quiet. Patience is part of training. They know from past experience, when need for action does come, it can come fast and urgent. There we are. A new audio return from a different moving target. This sound is characteristic. Notice how different from the previous sound. Trained radar operators would recognize it immediately, but make no snap judgment. The rule, take time to make sure, then act fast. In goes the report. A concentration alpha alpha one zero two. A moving target consisting of sound and sight recognition. At this sound, the picture of this moving target will pop into the trained operator's mind. The radar operator in the set's shelter can be trained to visualize the cause of the sound when he hears an audio return. Then, with the report on the way, the operator continues his mission at the next area of interest. Alpha alpha one zero three. What does the map tell us about this approach point? Crossroads under night skies. Clear terrain on one side. Sparse cover on the other. All is quiet. All is still. No moving targets so far. The operator will observe this point for a reasonable time. Then, should it produce no targets, it is time to move to the next approach. But not this time. From the memorized catalog of audio returns, this exact sound fits only one certain type of moving target. Train the mind to react like this screen, so that when the ear hears, the mind's eye sweeps back and almost instantaneously arrives at the correct picture. Report the information. Then, go on with the mission. Alpha alpha one zero four. Build a catalog of audio returns. Slight variations may develop in similar moving targets, and even in the radars themselves, but will not interfere with target identification. Here's a Y-shaped road junction. Nothing moves. A moving target could approach from any direction. Here it comes, down the main highway. Picture this moving target. Prepare to report approaching road junction is a... Now what's this? Audio returns from moving targets usually do not change, right in the middle of a highway. Only a very well-seasoned operator could identify so quickly this not-too-common audio return, and come up with this correct answer. This picture especially is one to remember, connected with this audio return. The maneuver here may not be a common one, but is an example of what might be done to receive an operator when an enemy commander believes his unit might be under radar observation. Quick identification, even of the unusual, is all in the night's work. So, on to the next. Concentration, alpha alpha one zero five. Here the map indicates rugged terrain with one long road. No moving targets. Let's see how the radar operator handles this one. The loudspeaker indicates no sign of action at this point. Nothing but uncommunicating silence. Never take silence for an answer. Check the radar controls. Is the speaker turned up? Be ready. That's better. Under combat conditions, this sound will be heard often. Present-day warfare will place this type of moving target on almost every passable highway. Here's the reason the audio return from this target is different from those previously heard. When the radar sets shelter, the operators will be going through the routine. Recognize, report, move on to the next assigned point, alpha alpha one zero six. A long road sloping down from the crest of a high hill. This exposed approach is where they must come. When they do, the radar beam must pick them up. Was the eye quick enough to catch that dark bulge moving at the crest of the hill? The radar caught the movement immediately. Notice the report is not yet being sent in. There's a good reason. From the nature of this target, there may be more than one of them entering and leaving the radar beam. Three. Four. Five. Report. Here they are. One follows the other at evenly spaced intervals. Once again, learn to associate sound and sight. This audio return with sight of this particular moving target. Let's recall briefly different audio return characteristics which identify different types of moving targets. See how many can make a perfect score of telling what audio return comes from which moving target. From sound alone, would you know it was this moving target? From this sound, did you picture this target? And from this, did this come to mind? Now this sound for this target? For this one? If from this sound, your mind's eye recalled this moving target, then you've made a perfect score for target identification. If not, practice makes perfect. Quick, sure target detection, overcoming poor visibility, can make the difference between success and failure.