MIL-DTL-55535A
4.13.5 Salt atmosphere (see 3.8.5). The completely assembled equipment shall be exposed to a 20
percent salt spray solution, in accordance with method 101 of MIL-STD-202 for a period of 48 hours.
4.13.6 Blast test (see 3.8.6). Each earphone and microphone element being tested shall be mounted
on the carriage of the U. S. Navy Simulated Gun Blast Equipment, in accordance with Bureau of Ships
Drawing SK-N-864 with the front edge of the earphone or microphone element in the test plane, and with
its axis coincident with that of the explosion chamber. The earphone and microphone element shall be
subjected to 30 rounds of blast at a peak pressure of 9.5 pounds per square inch.
4.13.7 Vibration test (see 3.8.7). The complete equipment shall be subjected to the vibration test in
accordance with method 201 of MIL-STD-202. The equipment shall be mounted in a horizontal position,
and shall be vibrated in a direction perpendicular to the plane of the earphone and microphone for a
period of 5 hours.
4.13.8 Bounce test (see 3.8.8). The equipment shall be tested on the package tester, as made by the
L.A.B. Corporation, Skaneateles, New York, or equal, as follows:
a. Cover the tester bed with a panel of 0.5 (½) inch plywood, with the grain parallel to the drive
chain. Sixpenny nails with the heads below the surface shall be spaced at 6-inch intervals around
all four edges and at 3-inch intervals in a 6-inch square in the center.
b. Place the equipment on the bed of the package tester. Limit the lateral motion, by wooden
fences, to not more than 3 inches and not less than 1 inch. Additional barriers may be used to
prevent tumbling, provided that the fore-and-aft motion of the equipment against the back stop is
not restrained.
c. Operate the package tester, shafts in phase, for a total of 3 hours at 284 ± 2 rpm. Turn the
equipment at the end of each 30 minutes so it will rest on a new face.
degradation not to exceed 3 dB.
4.13.9 Shock drop test (see 3.8.9). The shock drop test shall be performed as follows:
4.13.9.1 Microphone: The microphone M-138/G shall be dropped at random 12 times, from a height of
6 feet, onto a concrete floor.
4.13.9.2 Earphone elements. The earphone elements H-269/G, mounted in the ear-cushions, shall be
dropped at random 12 times, from a height of 6 feet, onto a concrete floor.
4.13.9.3 Switch microphone. The switch housing assembly SA-1552/G mounted on a CVC helmet
shall be dropped at random 6 times, from a height of 4 feet, onto a concrete floor.
4.13.9.4 Reassembled equipment. The equipment shall operate satisfactorily after being dropped and
shall not suffer any degradation in performance of more than 3 dB for the microphone element and the
earphone, when tested in accordance with 3.6.1 and 3.7.1 respectively. There shall be no evidence of
breaking, cracking, or physical damage. Minor chipping shall not be considered a failure.
4.14 Dielectric strength and insulation resistance (see 3.10.1). A potential of 500 volts (rms) 60 cycles
shall be applied between any exposed metal parts of the switch (including the mounting screws and plate
if used) and control circuit contacts of the terminating plug-connector. The duration of voltage application
shall be 10 seconds. During the test there shall be no evidence of insulation breakdown and at the
conclusion of the test, the insulation resistance shall not have decreased to a value below 1 megohm.
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