The cable covered by this specification is intended for use in extensive electrical and electronic applications in protected areas. The above cables are not intended for use as portable cables, to be laid in the open where they may be subjected to vehicular traffic and direct burial. The cables described in this specification will provide flexible single shielded and multi-conductor cable for use within tunnels, wire ways, instrument racks, and conduits within the electronic equipment, trailers, or buildings and in protected runways between building. The cable will be used for data transmission, synchronizing pulses, audio and video signals, control power, radio frequency signals, and operating power for electronic equipment.

Table XV may be used as a guide to the selection of the basic wires designated A through E, and H. The values given are for engineering guidance only and are not intended to be specification requirements or firm limitations.

Where the cable is to be striped back and the individual insulated wires are exposed and may be subject to some mechanical abuse, it is suggested that wire designated M be used for sizes 24 through 12. Wires M and P may be used with conductor temperatures of 105°C and any combination of ambient temperature and current so that this conductor temperature is not exceeded. A life of approximately 3 months may be expected with conductor temperatures as high as 115°C and a life of approximately 1 week may be expected with conductor temperatures as high as 135°C. Wire M and P should not be used where it is expected that the exposed single conductor at cable ends will be bent or flexed at temperatures below minus 10°C in service and installation.

Type N wire may be used where handling bending and flexing of the individual conductors beyond the stripped back cable sheath may be experienced at temperatures as low as −55°C. The electrical properties of this insulation makes it suitable for the transmission of pulses with steep wave fronts, data transmission, video and radio frequency power. It is superior electrically to M and P wires, since the insulation resistance is several million megohms per thousand feet, its power factor is less than 0.005, and its dielectric constant in the order of 2.25 resulting in a low loss, low capacitance insulated wire. Provision is made for increasing the wall thickness of the polyethylene insulation to further reduce capacitance when required.

Wire types designated D and E should be used where reliability is of utmost importance. The desirable features of M, P, and H are combined in D and E wire. Maximum conductor temperatures up to 200°C are permissible (consistent with proper component jackets, tape and filler material, and sheath material). Wires D and E may be bent and flexed as a single conductor at temperatures as low as −210°C (liquid nitrogen or liquid oxygen spillage). Wires D and E have somewhat better electrical properties than N wire. The power factor is in the order of 0.0002 and the dielectric constant in the order of 2.0 thus giving improved performance where low capacitance and low loss is necessary. Provision is made for increasing the wall thickness of the insulation to further reduce capacitance when required.

The coaxial cable should be used when dictated by the radio, or audio frequency circuits, or for data transmission when the electrical properties of this type cable are necessary.

These wires have a tough mechanical outer coating over the primary insulation. This jacket is considered necessary because of the physical abuse presented to multiconductor cable during manufacture and installation and is particularly necessary where the wires are to be shielded or in contact with other shielded wires, to prevent small broken strands in the shield from penetrating through the relatively soft primary insulation and causing circuit failure. The polyamide specified is that which has been used for several years successfully in electronic and aircraft type wire for electrical purposes and has very low moisture absorption with desirable electrical properties.

Table XVI may be used as a guide in the selection of component jackets. The values listed are for engineering guidance only and are not intended to be specification requirements or firm limitations.

Polyamide jackets are intended to provide shield isolation where shields are carried at ground potential for small components. Polyamide jackets are not permitted for use except over shields because the polyamide component jacket would adhere to the polyamide jackets over the individually twisted pairs or triples and make it impossible to separate and properly strip the twisted component group. Further, this type of jacket is not allowed on diameters over ¼ inch because of the tendency of polyamide when applied over large diameters to stretch when bent, and wrinkle when straightened again. With repeated working, these wrinkles may easily become cracks.

Polyvinyl chloride jackets are generally recommended for polyvinyl chloride insulated wires to be used in applications where ambient temperatures do not exceed 90°C and maximum conductor temperatures do not exceed 105°C for continuous use. Polyvinyl chloride jackets are suitable for short time use with polyvinyl chloride insulated wire with conductor temperatures as defined in 6.1.1.1. Polyvinyl chloride shall not be used in aerospace applications.

Polyethylene jacket is recommended where polyethylene insulated wire is used since it is compatible with maximum and minimum operating temperatures as defined in 6.1.1.2 and permits operation and handling at low temperatures of the complete component with a good degree of flexibility.

Fluorinated ethylene propylene jacket is recommended for polytetrafluoroethylene insulated wire where the advantage of the high operating temperature is desired. Fluorinated ethylene propylene jacket is suitable for operation up to 200°C for continuous service, and is satisfactory for use where the component must be handled at temperatures as low as minus 85°C.

Glass braid jacket is recommended for use only on single shielded constructions where protection is needed between the basic insulation and the shield. It is recommended for use with polyvinyl chloride insulated wires.

Table XVII may be used as a guide to the selection of a sheath. The values given are for engineering guidance only and are not intended to be specification requirements or firm limitations.

Polyvinyl chloride is suitable for ambient temperatures up to 90°C for continuous service and is suitable as a jacket for polyvinyl chloride insulated wires within the high conductor temperature limits set forth in 6.1.1.1 for short time use. If the cable is to be bent or flexed at low temperatures, extreme caution should be used with this style of sheath. It is not recommended that polyvinyl chloride sheath be used when the cable is to be handled at temperatures below minus 10°C. Even though a cold bend test at minus 40°C is provided in the specification, this test is only a comparison for quality control purposes between various types of polyvinyl chloride which might be used and an assurance of proper extrusion techniques, and the test does not represent the physical use that the cable in the field may get by manual handling. Polyvinyl chloride sheath provides a tough abrasion resistant outer covering for the cable. Polyvinyl chloride shall not be used in aerospace applications.

Polyethylene is suitable for operation over the temperature range indicated in 6.1.2.3 for polyethylene jackets. Polyethylene gives a tough highly abrasion resistant outer coating and retains flexibility at low temperatures.

Polychloroprene sheaths are intended for general purpose use between the temperature range of −55°C and +75°C. If the cable must be handled in any degree at low temperatures, polychloroprene would provide a more flexible cable than any of the other sheaths.

Florinated ethylene and polytetrafluoroethylene sheaths are intended for the outer covering of cable to be operated at temperatures above those permissible with polyvinyl chloride, polyethylene, and polychloroprene sheaths.

Polyamide sheath is intended for the outer covering on single shielded cables needing a tough mechanical outer layer.

Glass braid sheath is intended for the same use as polytetrafluoroethylene but for applications which need temperatures above 110°C.