(4) When previously produced models of this equipment did not use non-
repairable subassemblies, the design shall not be changed to employ
nonrepairable assemblies without the approval of the procuring
Nonstandard Parts and Materials Approval - Approval for the use of
nonstandard parts and materials (including transistors and diodes) shall be obtained as out-
lined in Specification MIL-E-54oo.
Microelectronic Modular Assemblies - When used, microelectronic
modular assemblies shall be described by a contractor procurement specification and must
be approved by the procuring agency. Microelectronic modular assemblies (microelectronic
circuits) (MICS) shall be contained within maintenance modules (for example, on printed
circuit cards). The choice of microelectronic modular assemblies shall be based on at least
two sources of supply, which can be used interchangeably.
Modules, Maintenance - The electronic portions of the equipment shall
be divided into maintenance modules (see Specification MIL-S-23603). Maintenance modules
shall normally be considered repairable.
Microelectronic Interchangeability - Microelectronic circuits (MICS)
shall be interchangeable at the MIC level, or at the maintenance module level when approved
by the procuring activity (see 6. 13).
Design and Construction - The equipment shall conform with all the
applicable requirements of Specification MIL-E-5400 for design, construction and workman-
ship, except as otherwise specified herein.
-- tal Weight - The total weight of the equipment, excluding cables, shall
be a minimum consistent with good design and shall not exceed 3.5 ounces.
Operational Stability - The equipment shall operate with satisfactory
performance, continuously or intermittently for a period of at least 1,000 hours without
the necessity for readjustment of any controls which are inaccessible to the operator during
Operati ng Life - The equipment shall have total operating life of 10,000
hours with reasonable servicing and replacement of parts. Parts requiring scheduled re-
placement shall be specified by the contractor.
Reliability in Mean Time Between Failure (MTBF) - The equipment shall
have 2,000 hours of mean (operating) time between failures when tested and accepted as
outlined under the requirements of 4.4.3.
Interchangeability of Reordered Equipment - For reordered equipment
interchangeability shall exist between units and all replaceable assemblies, subassemblies,