MIL-DTL-3661D
3.4.3 Screw threads. Screw threads on externally threaded parts, or parts subject to replacement or
removal, shall be in accordance with Handbook H28. Threading of non-metallic parts will not be permitted unless
otherwise specified on the specification sheet (see 3.2).
3.4.4 Anti-rotational means. Lampholders, indicator lights and indicator-light housings shall be designed
with an anti-rotational mounting means.
3.4.5 Panel accommodation. Unless otherwise specified (see 3.2), indicator lights and indicator-light
housings shall be designed to accommodate panels up to .187-inch in thickness using applicable mounting hardware
furnished. Mounting flanges shall be of the fixed type.
3.4.6 Current-limiting resistors. Current-limiting resistors used for neon indicator lights and housings shall
have a tolerance not to exceed 20 percent and the applicable ohmic value shall be as specified (see 3.2). The
resistor shall be physically located internally to the indicator light or indicator-light housing.
3.4.7 Press-to-test operation. When specified (see 3.2), the light shall be such that the lamp may be tested
by pressing on the lens of the assembly. When the pressure is released, the test circuit to the lamp shall be opened
and the lens assembly shall return to its normal position.
3.4.8 Lamp circuitry. Lampholders, indicator lights, and indicator-light housings shall be designed with an
electrically isolated lamp circuit.
3.4.8.1 Lamp accommodation (not applicable to non-removable lens assemblies). Panel mounted indicator
lights and indicator-light housings shall be designed so that the lamp(s) can be replaced from the front of the panel.
No tools of any type shall be required to replace the lamp (s).
3.4.8.2 Plug-in cartridge type lamps. Indicator-light housings using cylindrical plug-in lamps shall be
designed to accommodate lamps in accordance with MS18235, MS18236, MS18237 and MS18238. Current limiting
resistors required for neon lamps shall be built into the lamp cartridges.
3.4.9 Lenses.
3.4.9.1 Lens fabrication. The lens viewing area (window) shall be secured to a threaded metal bushing, as
applicable (see 3.2).
3.4.9.2 Color. The lens color shall be in accordance with FED-STD-3 or SAE-AS25050, unless otherwise
specified (see 3.2), and as follows:
3.4.9.2.1 Symbol C (colorless) . Colorless is defined as a lens which does not change the color coordinates
(±.01) of the calibrating lamp when measured from the front of the lens.
3.4.9.2.2 Symbol B (blue). The blue color shall be within the boundary formed by the interconnection of
the points shown for the chromaticity coordinates.
Point
X - Axis
Y - Axis
1
.065
.220
2
.082
.268
3
.154
.220
4
.165
.270
3.4.9.2.3 Symbol W (white), symbol Y (yellow), symbol E ( red aviation). White, yellow and red aviation
colors shall be in accordance with category I (aviation colors).
3.4.9.2.4 Symbol G (green), symbol R (red). Green and red colors shall be in accordance with category II
(identification colors).
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