MIL-DTL-55668 Cord, Electrical; Audio, Subminiature \(Retractile And Straight\)This specification covers subminiature audio helical retractile cords and straight cords with either stranded wire or tinsel wire conductors, for accessories associated in for the use with microphone, telephone, switchboard, and associated communication equipment. These cords are intended for operations at audio frequencies and temperatures from -55 Degrees C to +85 Degrees C with a high degree of flexibility. Each retractile cord is designed for extension in normal service up to 6 times its nominal retracted helical length.

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MIL-DTL-55668D

3.2.2 Tinsel wire. Tinsel wire shall meet the requirements type IV tinsel electrical wire, having an overall

dimension of 0.022 inch (.56 mm) � 0.002 inch (.05 mm) and a breaking load minimum of 10 pounds (see

3.3 Insulation. The insulation for both stranded and tinsel wire conductors shall be a crystalline ethylene-

propylene copolymer thermoplastic meeting the requirements of ASTM D4101. Insulation removed from

insulated conductors of finished cords shall meet the requirements of ASTM D1248 with the following

exceptions:

a. Cold bend shall be performed at -55 C.

b. For insulation removed from tinsel conductors, the ultimate elongation shall be 250%

minimum, and the tensile strength shall be 2,500 PSI minimum.

When tested for heat shock; there shall be no evidence of cracking.

3.3.1 Insulation wall thickness. Wall thickness at any section of insulation shall be nominal .007 inch

(.178 mm); minimum .004 inch (.102 mm).

3.3.2 Dimensions of insulated conductors. The diameter of the insulated stranded and tinsel conductors

shall be .035 inch (.889 mm), +.004, -.002 inch (+.102 mm, -.051 mm).

3.3.3 Insulation colors. Color of insulation shall conform to MIL-STD-104, class 1. The colors of

individual insulated conductors in a core complement shall be in the following sequence:

Yellow

Black

White

Blue

Red

Purple

Green

Brown

Orange

10.

Gray

3.4 Fibers and yarns. All synthetic yarns and fibers employed as servings, binders, fillers, cores for tinsel

strands and wires, and staycords shall be as specified herein.

3.4.1 Fillers. Filler yarn shall be used between insulated conductors to form an essentially circular

cross-section core and provide a slippage between the insulated wires. Fillers shall be a yarn conforming

to MIL-C-572 type PSTR (polyester) or type CTA (cellulose triacetate), or a polypropylene yarn or twisted

polypropylene film.

3.4.2 Staycord. Staycord shall consist of a polyaryl-amide fiber conforming to MIL-C-572 type PAA. The

cord shall have a minimum breaking strength of 20 pounds for cords of 2, 3, and 4 conductors, and 30

pounds for cords of 5 to 10 conductors. The filaments of the staycord shall be bonded together with a

fungus-inert adhesive in order to facilitate knotting during termination of the finished cord.

3.4.2.1 Center core. If necessary to provide a center core larger in diameter than the staycord, a filler

material as specified in 3.4.1 shall be served around the staycord.