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.

When we talk about RJ45 ("Registered Jack" 45) we refer to a telecommunications network interface for wired connection of voice and data equipment.

This connector has 8 pins or connections and may have a specific category depending on the data transfer speed and bandwidth (category 5e, 6, etc.)

The common application is their use in Ethernet network cables under TIA/EIA-568-B standard that defines the arrangement of pins (pinout), but can also be used for other applications.

- Direct pin diagram:

EIA-568A
Pin No.1: WHITE-GREEN
Pin No.2: GREEN
Pin No.3: WHITE-ORANGE
Pin No.4: BLUE
Pin No.5: WHITE-BLUE
Pin No.6: ORANGE
Pin No.7: WHITE-BROWN
Pin No.8: BROWN

EIA-568B
Pin No.1: WHITE-ORANGE
Pin No.2: ORANGE
Pin No.3: WHITE-GREEN
Pin No.4: BLUE
Pin No.5: WHITE-BLUE
Pin No.6: GREEN
Pin No.7: WHITE-BROWN
Pin No.8: BROWN

- Schematic of crossed pins:

The crossover cable has one end with EIA-568A scheme and the other one with EIA-568B.

or fed and enables easier application of uninterruptible power supplies (UPS) to ensure operation 24 hours a day, 7 days a week.

UTP cable is standard twisted pair is referred by its acronym UTP (Unshiedld Twiested Pair/Unshielded Twisted Pair). The major advantages of this cable are its low cost and ease of handling. Its main disadvantages are a higher error rate compared to other cable types and their limitations to work at high distances without regeneration. FTP is a type of cable caracteriza that each twisted pair is uniformly during creation. A comprehensive screening of all pairs is performed by a apantallante outer sheet. This technique allows to have similar characteristics to the shielded cable. STP is characterized by that each pair is covered with a metal mesh, in the same way that the coaxial cables, and the set of pairs is coated with a sheet apantallante. Referenced frequently with their acronym STP (Shield Twisted Pair/Shielded Twisted Pair)