SCANNING

1. In telecommunications systems, examination of traffic activity to determine whether further processing is required. Note: Scanning is usually performed periodically. 2. In television , facsimile , and picture transmission , the process of successively analyzing the colors and densities of the object according to a predetermined pattern. ( 188 ) 3. The process of tuning a device through a predetermined range of frequencies in prescribed increments and at prescribed times. Note: Scanning may be performed at regular or random increments and intervals. ( 188 ) 4. In radar and radio direction-finding , the slewing of an antenna or radiation pattern for the purpose of probing in a different direction. Note 1: In radar, scanning may be mechanical, using a rotary microwave joint to feed the antenna, or electronic, using a phased array of radiators, the radiated pattern ( beam ) of which depends on the relative phases of the signals fed to the individual radiators. Note 2: In civilian air traffic control radar, scanning usually implies continuous rotation of the antenna or beam about a vertical axis. In military radars, scanning may occur about other than a vertical axis, and may not encompass a full 360°.