A rack is a metal support designed to house electronic, computer and communications equipment. The measures for the width are normalized to be compatible with most equipment manufacturers. They are also called racks, cabinets, cabinets or closets. Each column has holes at regular intervals called U rack units (Pictured: 4) grouped in threes. The height (Pictured:5) of the racks is standardized and external dimensions of 200 mm by 200 mm. Being normal that from 4U to 46/47U height width types (Pictured: 7). Standard 600 mm or 800 mm Types of background (Pictured: 6) The depth of the frame is not standardized, as this flexibility is granted (Pictured: 8) to the equipment. The most common are: - 450 mm - 600 mm - 800 mm - 900 mm - 1000 mm - 1200 mm Type 19-inch rack can find various types of 19-inch rack. Rack Mural (Pictured: 2): Used to accommodate electronic network. They are the smallest and are anchored to wall. Rack Pie (Pictured: 1): They are used primarily for servers, UPS and network electronics. Open Rack (Pictured: 3): Open Rack Racks are available only modelsstructure, eliminating doors and other accessories.

There are several cabinet heights according to the needs of the installation, this height can be measured in rack units (U).

Each rack unit or U is the distance between each horizontal separation to place the different accessories inside the rack. This distance is 1.75 inches that is equal to 4.4445 cm high.

For example, if we say that a rack is 8U we will understand that it has 8 units to install device orAccessories of 4.44 cm in height.

Normally these accessories, like trays, guides, strips, etc. Occupy a unit of U (1U), but we can find that other devices or accessories occupy more units, for example can be a rack box to install a PC, a UPS, etc. It can be said that there is also a half unit of U (0.5U), in this case, two units could be installed in a rack unit.

As far as I knowEndo the units of rack that occupy the devices that we are going to install we will know the height that we need for our rack.

The size of the rack unit (U) is based on the standard specification for racks defined in EIA-310.

When carrying out an electrical installation or electrical circuit several factors must be taken into account, one of them is the selection of the appropriate cable. According to the installation and the use of the same we can find different diameters that support different loads. The cable section will also help us not to overheat our installation, since the larger the section, the greater the thermal resistance.
In the following table poWe can see the corresponding load supported for the different sections of cables.

As it is common in installations we can find a standard of colors in the electric cables.

These regulations help at a glance to understand the connection and the resolution of possible faults or failures.

Below we attach the color/cable relation for electrical installations.

1. The ground wire can be identified in several ways:
• Green cable.
• C cablegreen smell with a yellow line.
• Cable without insulation.
2. The neutral wire will be blue.
3. The phase cable can be identified in several ways:
• Any color different from neutral or earth.
• Black insulation.
• Brown isolate.
• Gray insulation.

The insulating or insulating tape is a fundamental element when making a repair or performing an electrical installation. The insulating tape will help us to protect and insulate the electrical cables from possible crossings or contacts between them or with other elements, guaranteeing that the connection is well insulated avoiding possible short circuits.
Its use is very simple, since being a flexible material allows us to apply it with comfort.
To achieve a perfect union, it is recommended that we wrap the tape covering half the cable and half over the joint, stretching the tape slightly while rolling obliquely.

• For the ground wire, colored insulation tape will be used:
• Green.
• Green with a yellow line.
• For the neutral cable, blue insulating tape will be used.
• For the cable the phase isYou can use any other color:
• Any color different from neutral or earth.
• Black insulating tape.
• Brown insulating tape.
• Gray insulating tape.

VAC would be the abbreviation of Volt Altern Current which would be translated Volts of alternating current. The difference between VDC is that its sinusoidal oscillation achieving a more efficient energy transmission.

The alternating current is the energy that we receive in our homes, it is generated in the power plants by means of alternators.

The intensity of this type of current varies with time, and changes direction 50 times throughsecond (50hz). The generated voltage changes in the form of sine wave so it is not constant.

In the image:

1. Current by pulsations.
2. Direct current (DC).
3. Alternating current (AC).
4. Variable current.