Drawing numbers may be used to identify
microfilm that may be available on the equipment or
assembly. Some large assemblies are illustrated in IPBs
but are not broken down sufficiently to show identifying
data for their component parts. By obtaining the
d r a w i n g n u m b e r o f t h e l a r g e r i t e m a n d
cross-referencing it to the applicable microfilm, you can
obtain sufficient identifying information for the
component part.
Specification Number
A specification number is assigned to documents
describing the characteristics and properties of material
purchased by the Federal Government. These
specifications are used by purchasing officers to ensure
that all of the requirements for the material are met.
Specification numbers on some support equipment are
particularly useful when you are trying to procure
component parts.
Some equipment has a nameplate attached that
provides such information as the manufacturer's name
or code, make or model number, serial number, size,
voltage, phase, NSN, and so on. This information is
particularly helpful when you are requesting material
that is not subject to the Federal Catalog System.
Most equipment purchased for Navy imaging has
with it an instruction book or a technical manual that is
published by the manufacturer. You can often use it to
help you identify specific parts, since this technical
manual often includes parts lists, detailed drawings, and
Illustrated Parts Breakdown (IPB) publications are
an important source of information, particularly for
ordering specific support-equipment parts. Used
properly, they provide the information necessary to
identify a part number. In some cases, IPBs provide
cross-reference data that can be used when the prime
item requested is not in stock.
An IPB is prepared by the manufacturer for most
major items of imaging equipment and accessories.
The IPB is designed to enable supply and maintenance
personnel to identify and order replacement parts for
equipment. Procurable assemblies and detail parts are
illustrated and listed for quick identification of
assemblies and their component parts. The items are
arranged continuously in assembly breakdown order.
The illustrations are placed as near as possible to their
Although slight variations in format exist among
the various IPBs, each one includes the following major
The INTRODUCTION includes general
information about the equipment, contents of the
publication, and instructions for use. You should refer
to the introduction before attempting to use an
unfamiliar IPB.
a breakdown of the complete unit into major
components, systems, installations, assemblies, and
detail parts. Generally, parts are indexed in disassembly
order. In some instances, assemblies or installations are
shown in assembled form in one figure and the detail
parts are illustrated in another figure.
The NUMERICAL INDEX lists part numbers in
alphanumerical order, and each part number is
cross-referenced to the figure and index number where
it is shown. This section also shows the total quantity
of each part used in the equipment, material source
code, and NSN, when applicable.
in alphanumerical order, reference designators
(example: B1, J1, K7, and so on) on schematic and
wiring diagrams. The index also lists part numbers and
index numbers to indicate where the parts are located in
the IPB.
The Consolidated Master Cross-Reference List
(C-MCRL) is designed to provide a cross-reference
from a reference number, such as a manufacturer's part
number, a drawing number, a design control number,
and so on, to an assigned NSN. Part I of the C-MCRL
is designed to assist you in identifying items in the

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