Cable shielding

Fluorocarbons (PTFE, FEP, PVF2) Powder, emulsions Excellent high temperature properties. TFE to 500 F. FEP is easier to mold, but maximum use temperature is 400 F. Nearly inert chemically. Nonflammable. Loading with conductive filler improves creep resistance. Low coefficient of friction. High-temperature cable shielding, gaskets, heat-shrinkable tubing. 

Polyimides Powder, solutions Excellent high temperature properties, 400 to about 700 F. Difficult to process. High-temperature cable shielding, conductive film. 

Vinyls Powder, pellets, General-purpose material. Many Cable shielding,... 

LLDPE has most of the good features of both LDPE and HDPE— strength, flexibility, clarity, good dielectrics, and high/low temperature stability (for wire and cable shielding). 

The studies were carried out in air-conditioned areas from which hazards of accidental injury had been eliminated as thoroughly as possible (e.g., glass panels in doors were replaced with wood, electric outlets and cables shielded, and sharp comers padded). Beds and collet, messing and recreational facilities were provided within the research areas. The research was conducted under surveillance of qualified physicians, who administered all injections or oral doses of the test substances. When volunteers were exposed to inhalation of vapors or aerosols, the concentrations of these substances in the air to be breached by the subjects were established by appropriate personnel. Breaching of the contaminated air by the volunteers was observed and supervised by physicians. After an exposure to an agent, the volunteers were observed continuously for 8-24 h, and then Intermlctently for up CO 14 d. In a few cases, followup studies were made 6 mo or more after the exposure. 

Many manufacturers put pretty plastic insulating collars on their BNC panel mounts. Disaster There is no good ground connection at the enclosure wall and the cable shield radiates into the box. There is only one solution take the panel mounts apart and get rid of the insulating collars. Figure 2 shows where common problems occur. 

EMI shielding of polypyrrole in porous host polymers has also been reported [24]. A new type of measurement of shielding properties of polypyrrole has been recently published [25]. The method applies far-field conditions with a TEM mode inside a specifie waveguide. Evolution of SE with thickness and conductivity is presented. One example of an application has been given with cable shielding by polypyrrole [26],... 

Fig. 7.54 Correctly designed RF shielding. The noise current flowing through the cable shield is diverted outside the housing...

Fig. 7.55. .Emergency repair" of a poorly designed RF shield. A copper foil wrapped around the cable forms a capacitor with the cable shield and diverts a part of the noise current...

BP Chemicals have introduced a new technology for silane cross-linking in low-voltage cable insulations to produce more uniform cross-linking and greater shelf-life. The new silane-linked polyethylene compounds can be run on conventional extrusion equipment. The company has also produced a strippable double layer cable shield in cross-linkable polyethylene for medium voltage cables. 

Uses For extrusion coating applies, incl. foil-containing shampoo, toothpaste, towelette, condiment, and misc. non-food pouches and sachets, snack structures, toothpaste tubes, cable shield wrap, aseptic and hot-filled cartons other foil, metalized film, or paper coatings as heat seal or tie layer food-contact polymers Regulatory FDA 21 CFR 177.1330 compliant Properties Pellets sp.gr. 0.93 melt flow 10.0 dg/min f.p. 84 C m.p. 103 C Vicat soften, pt. 86 C 8.7% methacrylic acid Precaution Do not use in medical applies, involving permanent implantation in human body Nucrel 1214 [DuPont]... 

P. Kathirgamanathan, Novel Cable Shielding Materials Based on the Impregnation of Microporous Membranes with Inherently Conducting Polymers. Adv Mater 1993, 5, 281-283. 

Squires, C. 1995. Predicting and controUing PCB radiation, emf-emi control Journal (Sep.-Oct.) 17. Stephens, E. 1994. Cable shield outside the telco plant, emf-emi control Journal (Jan.-Feb.) 18. 

White, D. 1995. How much cable shielding is required, emf-emi control Journal (March-April) 16. 

The choice of a particular network architecture will have a definite bearing on the choice of network adapter cards and less of an impact on the choice of media or network operating system. For instance, an ethernet network architecture requires ethernet adapter cards. As will soon be seen, it is the adapter card which holds the key, or media access control (MAC) layer protocol, which determines whether a network is ethernet, token ring, fiber distributed data interface (FDDI) or any other network architecture. Ethernet runs over thick or thin coaxial cable, shielded or unshielded twisted pair, fiber or wireless—clearly a wide choice of media options. 

Haynes, G. and Baboian. R., "Field Corrosion Testing and Performance of Cable Shielding Materials in Soils," MP, September 1989, pp. 68-74. 

When corrosion surveys have established the location and source of corrosion problems on a telecommunication cable plant, the next step is to establish mitigation measures. These measures can include placement of insulating joints to limit current pickup by the cable shield in cable entrance facilities (CEFs), some building entrances, vertical riser cables on telephone poles, and, under special conditions, in manholes. Most of these measures consist of placing low-resistance drainage bonds to return stray DC currents to their source without causing corrosion. If the stray current... 

RG. 4—Temperature-humidity cycling for cable shield bonding clamps. 

NACE International Publication IOC 198, "Technical Committee Report Corrosion of Cable Shielding for Telecommunica-... 

Gerhold, W. F. and McCann, J. P., Corrosion Evaluation of Underground Telephone Cable Shield Materials, Paper 31, CORROSION/76, NACE, Houston, TX, 1976. 

S] Generic Requirements for Cable Shield Bonding Clamps, Bellcore TA-TSY-001001, Bellcore, Livingston, NJ, 1989. 

To test for this condition, the receiver cable is disconnected from the EXT. Det. connector and held against it so the cable shield circuit is made but not the inner conductor circuit. The receiver output should be quite low. The cable is then connected normally and the R dial moved from the null position just sufficiently to duplicate the receiver output observed above. The magnitude of the R dial deviation is then a good estimate of the error caused by the leakage. 

For highly sensitive equipment, appropriate cable shielding should be provided, in particular for safety related I C items. 

Tarnishing and Cracking of Silver-Plated Copper Cable Shield.455... 

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