Electrical/Electronic Drawings, ContinuedInterconnectionInterconnection diagramsshow cabling between electronic units and how thediagramsunits interconnect. All terminal boards are assigned reference designation(shipboard)according to a unit numbering system.ReferencedesignationsA reference designation is a combination of letters and numbers used toidentify the various parts and components on electronic drawings, diagrams,and parts lists. Reference designations are assigned beginning with the unitand continuing down to the lowest level (parts).Units begin with the number1 and continue with consecutive numbers for all units of a set.Assembliesand subassemblies are assigned reference designators beginning with the unitnumber, the letter A to indicate an assembly or subassembly, and a specificnumber. Parts are assigned Reference designations for parts that consist of aunit and assembly or subassembly designation plus a letter or lettersidentifying the class to which the part belongs and a specific number. Foreach additional subassembly, another letter A and number are added to thepart reference designation.In the prints you work with the drawingsreference designation will comply with a system called the unit numberingsystem.Unit numberingThe unit numbering system is the reference designation system used tosystemidentify electronic systems that are broken into sets, units, assemblies,subassemblies, and parts. A system is defined as two or more sets and otherassemblies, subassemblies, and parts necessary to perform an operationalfunction or functions. A set is one or more units and the necessaryassemblies, subassemblies, and parts connected or associated together toperform an operational function.Figure 4-25 shows a five-unit set.Figure 4-25.—A five-unit set.Continued on next gage4-35
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