S.L. Type Cables: These cables are identical to H-type cables, except each of the three cores has its own lead sheath. This provision eliminates the necessity for the preceding overall sheath. The benefit of such a design is that the odds of a core-to-core failure are considerably reduced. Also, it allows for easier repair or replacement of any one core rather than having to replace the entire cable.
The S.L. designation comes from the initials of two of its inventors: Sanjay Lakhani and Larry Brinkman. It was introduced by Southern California's Pacific Telephone & Telegraph in 1990.
SL cables are commonly used in long-distance telephone networks to connect switching centers with other types of equipment such as remote terminals. They provide many advantages over H-type cables including lower weight per unit length, improved resistance to electrical interference, and reduced risk of short circuiting due to the absence of shared outer conductors.
In addition, SL cables can be identified by their different color codes for each of the three cores. Usually, these colors indicate the direction in which voltage is carried by each core. For example, red signals on white cores, white signals on red cores, and black signals on black cores. The exact code will depend on the manufacturer and type of cable being used.
SL cables are commonly available in lengths of up to about 150 meters (500 feet).
HT cables can have a multicore structure, which includes up to three cores. The primary distinction between the two types of cables: low-tension cables and high-tension cables is their electrical rating [1.1kV]. Cables with higher voltage ratings may have thicker insulation around the conductor wires.
There are also hybrid cables that combine characteristics of both low-tension and high-tension cables. They are usually used in areas where you have medium-high voltage but also need to minimize cable loss.
Cables are generally categorized by voltage level: low tension (LT), mid-range tension (MT), or high tension (HT). These categories refer to the maximum operating voltage that can be applied to the cable without causing damage to its insulation. For example, an LT cable can withstand 1,000 volts, an MT cable can handle 2,000 volts, and a HT cable can take 3,000 volts or more.
The term "cable" is often used interchangeably with "wire", but they are not the same thing. A wire is one strand of copper or aluminum within a cable. Cable has several strands of wire inside it for greater strength.
Cables are usually labeled with two numbers indicating their maximum usable voltage.
Coaxial, twisted pair, and fiber-optic cabling are the three most popular cable types used for Ethernet cabling. Twisted pair cable is the most common type of cabling in today's LANs, but fiber-optic cabling is becoming more prevalent, particularly in high-performance networks.
Twisted pair cable is the simplest to install and the least expensive. It consists of two wires that are wrapped around a core wire multiple times to create a tight spiral that provides shielding as well as data transmission capability. The number of twists determines the maximum data rate; more twists means faster transmission.
The other main type of cable used in Ethernet installations is called coaxial cable. This type of cable is made up of a central conductor surrounded by a tube of polyethylene plastic or aluminum. The cable can be solid or hollow, depending on requirements. Coaxial cable is very flexible and can be bent without breaking. It is this flexibility that allows you to move equipment around after you've installed it without removing the cable.
The third type of cable used in Ethernet installations is called fiber-optic cable. This type of cable is made up of several strands of glass or quartz fibers enclosed in a protective coating. Fiber-optic cable is capable of transmitting data at rates much higher than twisted-pair cable (50 gigabits per second vs 100 megabits per second), but it is also much more expensive than twisted-pair cable.
An alternating current cable (AC cable) is a factory-assembled arrangement of insulated conductors shielded by an overall flexible interlocking metallic armor (sheath). The metallic sheath can be composed of either aluminum or steel. Armored cable with an aluminum sheath is only suited for alternating current circuits. Cable with a steel sheath can carry both alternating and direct currents.
The individual conductors within the armored cable are made of copper or other metals. They are covered with insulation that prevents any contact between these conductors. Each conductor is surrounded by a layer of rubber or plastic which protects the conductor from external forces and prevents it from being damaged by repair work on neighboring cables. Finally, the whole assembly is contained in a metal case.
There are two types of AC cables: circuit-grade and appliance-grade. Both types of cable are intended for use with electrical equipment that could be damaged by an electric shock. Circuit-grade AC cables have more restrictive quality controls than appliance-grade cables and are designed to carry up to 100 volts at 20 amperes for 1,000 feet. Appliance-grade AC cables can handle up to 120 volts at 30 ampeers for up to 2,000 feet.
Both types of cable consist of one or more conductors surrounded by layers of insulation and protected by a metal shell.
3 1/2 core low tension cable: utilized for underground service connections. This cable is made up of 3 1/2 conductors, each covered with a thermoplastic insulation layer and a metal shield to provide protection from electrical interference. The 3 1/2 conductor size ranges from 0.0254 to 0.0284 inches in diameter.
The main advantage of using 3 1/2 core cable is that it can carry three times as much current as two-core cable of the same size, which reduces the number of required cables. It also has better resistance to environmental factors such as heat and cold when compared to single- or two-core cables. Three-core cable is more expensive than two-core cable but requires less space because there are fewer conductors to place inside the conduit.
Single-conductor cable includes one conductor within its insulation layer that is not enclosed by a metal shield. This allows for only one current to flow through the cable at any given time. Single-conductor cable is used when the location of the connection site makes it difficult or impossible to bury multiple cables.