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

Selection of basic wire.

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

Wire designated A and B.

These wire types have a tough mechanical outer coating over the conductor cable during manufacture and installation. This jacket is considered necessary because of the physical abuse presented to multiconductor cable during manufacture and installation. It 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.

Wires designated D and E.

Wires designated D and E should be used where reliability is of utmost importance. 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 -200 °C (liquid nitrogen or liquid oxygen spillage). The power factor is in the order of .0002 and the dielectric constant in the order of 2.0, thus giving improved performance where low capacitance and low loss are necessary.

Wire designated P.

Wire designated 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. This type wire should not be used where it is expected that the exposed single conductor at cable ends will be bent or flexed at temperatures below -10 °C in service and installation.

Selection of component jackets.

Table XV 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.

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 .25 inch (6.4 mm) because of the tendency of polyamide when applied over large diameters to stretch when bent and to wrinkle when straightened again. With repeated working, these wrinkles may easily become cracks.

PVC jacket.

PVC jackets are generally recommended for PVC 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. PVC jackets are suitable for short time use with PVC insulated wire (designator P) with conductor temperatures as specified in 6.1.1.3.

Selection of sheath.

Table XVI may be used as 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.

PVC sheath (designator A).

PVC is suitable for ambient temperatures up to 90 °C for continuous service and is suitable as a jacket for PVC insulated wires within the high conductor temperature limits set forth in 6.1.1.3 for short time use. If the cable is to be bent or flexed at low temperatures, extreme caution should be used with this type of sheath. It is not recommended that PVC sheath be used when the cable is to be handled at temperatures below -10 °C. Even though a cold bend test at -40 °C is provided in the specification, this test is only a comparison for quality control purposes between various types of PVC that might be used and an assurance of proper extrusion techniques; the test does not represent the physical use that the cable in the field may get by manual handling. PVC sheath provides a tough abrasion-resistant outer covering for the cable.

Polyethylene sheath (designator B).

Polyethylene is suitable for operation over the temperature range specified in table XVI. Polyethylene gives a tough highly abrasion-resistant outer coating and retains flexibility at low temperatures.

FEP (designator D) and PTFE (designator E) sheath.

FEP and PTFE sheaths are intended for the outer covering of cable to be operated at temperatures above those permissible with PVC and PE sheaths.