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

TABLE II. Properties of jacket material.

Property

Value

Unaged

Ultimate elongation, minimum average percent

175

with no value less than, percent

150

Tear resistance, minimum lb./in.

Cold tension recovery at -55 C, minimum percent

Hot tension recovery at 85 C, minimum percent

Free sulfur, maximum percent

.25

Tensile strength, minimum psi

1500

Set, maximum inch

.375

Tensile stress, (200 percent elongation, minimum psi)

300

Brittleness temperature, unaged, max, C

-55

Aged

Oxygen bomb, 95 1 hour at 70 C

Change in tensile strength, maximum percent

Change in elongation, maximum percent

Air oven, 168 1 hour at 100 C

Change in tensile strength, maximum percent

Change in elongation, maximum percent

Ozone resistance after oven-aging

No cracks

Brittleness temperature, after aging, max. C

-55

Torsional stiffness ratio, max

3.8 Requirements of the completed cord. The completed cord shall meet the requirements specified in

table III when tested under the applicable test paragraph, except that the extension or retraction

cords.