Figure 2-67.-Securing wire bundles in high temperature

cable strap and one that has a flat surface for

terminations are also necessary for efficient operation

identification of cables.

of the line.

The inner conductor may be either solid or stranded.

Installing self-clinching cable straps is done with

It may be made of unplated copper, tinned copper, or

a military standard hand tool (fig. 2-65). An

silver-plated copper. Special alloys may be used for

illustration of the working parts of the tool is shown

special cables.

i n figure 2-66. To use the tool, follow the

manufacturer's instructions. Do not use nylon cable

The dielectric insulating material is usually poly-

straps over wire bundles containing radio-frequency

ethylene or Teflon. Polyethylene is a gray, translucent

(RF) coaxial cable. Do not use nylon straps in areas

material. Although it is tough under general usage, it

where failure of the strap would allow the strap to fall

will flow when subjected to heavy pressure for a period

into movable parts or in high-temperature areas

of time. Teflon is a white opaque plastic material. This

(above 250F).

material will withstand high temperatures and will re-

main flexible at relatively low temperatures. It has a

HIGH-TEMPERATURE, PRESSURE-

peculiar quality in that nothing will stick to it, and it is

SENSITIVE TAPE LACING.-- High-temperature,

unaffected by the usual solvents.

pressure-sensitive tape should be used to tie wire

Braided copper is usually used for the outer con-

bundles in areas where the temperatures may go above

ductor; it maybe tinned, silver-plated, or bare. The outer

250F. Install the tape as follows (see fig. 2-67):

conductor is chosen to give the best electrical qualities

1. Wrap tape around the wire bundle three times,

consistent with maximum flexibility.

with a two-thirds overlap for each turn.

The protective insulating jacket is usually a syn-

2. Heat-seal the loose tape end with the side of a

thetic plastic material (vinyl resin). Neoprene rubber is

soldering iron tip.

generally used on pulse cable; silicone rubber jackets

are used for high-temperature applications.

RADIO-FREQUENCY COAXIAL CABLES

Armor is needed for protection. It may be braided

aluminum, or sometimes galvanized steel, similar to

that used on power cables.

RF cables may look like power cables, but they

require special handling and careful installation.

These cables are vital to the proper operation of all

SUMMARY

electronic equipment. They must be installed and

maintained with the greatest care.

In this chapter, we have discussed some of the

Flexible RF transmission lines (coax) are two-con-

more common types of switches, relays, and solenoids

ductor cables. One conductor is concentrically

used in the IC Electrician field. We have also

contained within the other, as shown in figure 2-68.

discussed the use of fuses, circuit breakers, and

Both conductors are essential for efficient operation

overload relays in protecting IC equipment.

of the transmission line. The proper connectors and

Additionally, we have identified electrical cables used

to supply power for IC equipment and the proper

procedures for installing and connecting cable to the

equipment.

Figure 2-67.-Securing wire bundles in high temperature

areas.

Figure 2-68.-Construction of flexible RF transmission line.

2-53