Electrical/Electronic Drawings, Continued
Interconnection diagrams show cabling between electronic units and how the
units interconnect. All terminal boards are assigned reference designation
according to a unit numbering system.
A reference designation is a combination of letters and numbers used to
identify the various parts and components on electronic drawings, diagrams,
and parts lists. Reference designations are assigned beginning with the unit
and continuing down to the lowest level (parts).
Units begin with the number
1 and continue with consecutive numbers for all units of a set.
and subassemblies are assigned reference designators beginning with the unit
number, the letter A to indicate an assembly or subassembly, and a specific
number. Parts are assigned Reference designations for parts that consist of a
unit and assembly or subassembly designation plus a letter or letters
identifying the class to which the part belongs and a specific number. For
each additional subassembly, another letter A and number are added to the
part reference designation.In the prints you work with the drawings
reference designation will comply with a system called the unit numbering
The unit numbering system is the reference designation system used to
identify electronic systems that are broken into sets, units, assemblies,
subassemblies, and parts. A system is defined as two or more sets and other
assemblies, subassemblies, and parts necessary to perform an operational
function or functions. A set is one or more units and the necessary
assemblies, subassemblies, and parts connected or associated together to
perform an operational function.
Figure 4-25 shows a five-unit set.
Figure 4-25.A five-unit set.
Continued on next gage