MIL-DTL-19648E
2.3 Order of precedence. In the event of a conflict between the text of this document and the
references cited herein (* except for related associated specifications, specification sheets, or MS
sheets), the text of this document takes precedence. Nothing in this document, however, supersedes
applicable laws and regulations unless a specific exemption has been obtained.
3. REQUIREMENTS
3.1 Specification sheets. The individual item requirements shall be as specified herein and in
accordance with the applicable specification sheet. In the event of any conflict between the requirements
of this specification and the specification sheet, the latter shall govern.
3.1.1 Relays not covered by specification sheets. Performance criteria shall be as specified herein and
in accordance with the individual service's or manufacturer's drawing. In the event of any conflict
between the requirements of this specification and the applicable drawing, the latter shall govern.
3.2 First article. When specified in the contract or purchase order, a sample shall be subjected to first
article inspection (see 4.4 and 6.3).
3.2.1 Inspection of relays not covered by specification sheets. Relays furnished under this
specification and not covered by specification sheets shall be products which have been tested and have
passed the inspection specified in 4.5.
3.3 Material. Material shall be as specified herein. However, when a definite material is not specified,
a suitable material shall be used which will enable the relay to conform to the performance requirements
of this specification. Acceptance or approval of any constituent material shall not be construed as a
guaranty of the acceptance of the finished product.
3.3.1 Metals. Metals shall be of a corrosion-resistant type or shall be plated or treated to resist
corrosion. Zinc plating, cadmium plating, or unfused pure tin plating shall not be used on internal parts of
hermetically sealed relays. Zinc plating or cadmium plating shall not be used externally. Unfused tin
plating shall have a plating thickness of 200 microinches minimum if used for external parts.
3.3.1.1 Dissimilar metals. When dissimilar metals (as defined in MIL-STD-889, paragraph 3.1) are
used in intimate contact with each other, protection against electrolysis and corrosion shall be provided.
The use of dissimilar metals which, in contact, tend toward active electrolytic corrosion (particularly brass,
copper, or steel used in contact with aluminum or aluminum alloy) is not acceptable. However, metal-
plating or metal-spraying of dissimilar base metals to provide similar or suitable abutting surfaces is
permitted. The use of dissimilar metals separated by a suitable insulating material is also permitted.
3.4 Design and construction. The relays shall be of the design, construction, and physical dimensions
specified (see 3.1 and 6.2.1).
3.4.1 Heater winding. The heater winding shall be electrically insulated from the case or frame.
3.4.1.1 Rated heater voltage (see 6.7.1). Rated heater voltage shall be as specified (see 3.1 and
6.2.1).
3.4.2 Contact arrangement and contact rating. Contact arrangement and contact rating shall be as
specified (see 3.1 and 6.2.1). The rating shall be specified in current and voltage, ac or dc; and type of
load, resistive, inductive, or tungsten lamp. For ac ratings, frequency shall be 60 Hz unless otherwise
specified.
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