Different types of cables have different functions and it is easy to view any cable as a single, working unit. But each cable is made of different layers, with each layer providing a different function. Learning how these pieces interact makes it easier to understand just how a cable works and what can be done to avoid damaging a cable.
Coax is one of the most common types of cable, having been in use for well over 100 years. While the technology has improved over time, the basic layout of coax cables is much the same today as it was at the time of its invention. Modern coax cables are most commonly used for television, radio, internet, and security camera connections.
The outermost layer of the cable is the jacket, designed to protect the more vulnerable inner components. Jackets are most commonly made from plastic and come in a few different varieties. Along with providing protection from outside elements, jackets also act as an outer insulator to contain any electrical or magnetic signals that leak past the other layers.
The next layer is the shield, which can be braided or foil. While the shield does help to keep the electrical cable of the signal in, it is more meant to keep other signals out. If a coax cable is near something else that puts out strong signals that can potentially cause interference, such as heavy power lines or a cell tower, the shield cuts down on potential problems.
Following that is the dielectric, an insulator that keeps the coax cable signal contained within the center conductor. Dielectrics are designed to minimize leakage, keeping the signal being transmitted through the cable focused and strong. They do help to keep outside signals from causing interference, but this is more of a secondary function since interference should not make it past the shield under ideal conditions.
The final section is the center conductor at the core of the cable. This is a conductive metal line (typically made from either copper or copper-clad steel) designed to transmit the signal going through the cable. A core can be solid or stranded. As the most important part of the cable, it is heavily protected by the first three layers. Damage to the other three layers can make a cable weaker, but damage to the conductor is more likely to break a cable outright.
Ethernet cable is similar to coax, with metal cores protected by several other layers. The key difference is that ethernet is made up of multiple smaller wires contained within the main cable.
Like coax and many other cables, the outer jacket of ethernet is mainly serves to protect the smaller, more vulnerable pieces inside. The jacket is most commonly made of plastic, with different types available depending on what kind of environment the cable will be exposed to.
If an ethernet cable is shielded, the shield will be located directly under the jacket. Shields on ethernet cable can be stuck to the jacket with some sort of adhesive, such as aluminum tape or mylar tape. Some even use a sticky gel; while the gel works great as an insulator, it can also be a bit messy to work with. Many ethernet cables also include a rip cord, a small fluffy bit of fiber designed to peel the shield back and expose the inner wires.
Inside the jacket, there are eight smaller wires. Each wire is color-coded so users can easily tell them apart. As an industry standard, these wires are paired off and twist around each other. This allows the otherwise flimsy wires to support each other and prevent damage as the cable bends, twists, and turns. It also keeps the wires lined up for the most common ethernet pinouts. These wires are covered with HDPE insulation, keeping the signals running through each wire separate.
The core of each wire is a metal conductor, which can be solid or stranded. These cores connect to the metal pins (contacts) on ethernet connectors in order to transmit signals. The cores are delicate and damage to them can weaken the signal transmission, or stop the cable from working completely. A signal tester can be used to check which internal wire is non-functioning.
Telephone cable is much simpler than many other types of cables. Simple flat telephone cords are typically used in areas where electrical interference is not an issue, like an office or living room. As a result, shielding is not always needed. The outer jacket still acts as an insulator but focuses just as much on keeping the internal wires lined up in a nice, evenly shape than anything else.
Like ethernet cables, telephone cables contain smaller individual wires that are color-coded. These colored cables are not always attached to connectors the same way; depending on the application they can use a straight or reverse pinout. The number of wires is not always the same either. Newer cables use six wires while older cords use four. Cords with more wires can handle additional lines when splitting a single cable between multiple phones, fax machines, and other devices.
Round versions of telephone cables also exist but tend to be used for specialized functions. These cables include functionality not found in standard telephone cables, such as double-shielding for Internet modem cables or UV (sunlight) and water resistance for outdoor/direct burial cables. Being round, the internal layout of these cables is more in line with the inside of an ethernet cable than other phone cords.