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.

Nowadays we all have in mind the importance of controlling and verifying the bills we receive in the stores. Thanks to the different security systems implemented and the renewal of protection systems in the new current tickets, it becomes increasingly difficult to falsify, but still an extra control is highly recommended.
Counting systems or banknote detectors use the combination of vArias detection technologies to check if the ticket is false or the ticket is true.
Among the detection systems we find from the simplest (pen) to machines that verify different characteristics of the ticket to verify their authenticity.
The most common detection systems are:

1. LABEL: Simply mark the ticket to check. If the mark is displayed in black, the billetAnd is false.

Detecting machines: The most reliable, as they can combine different detection technologies such as:

1. UV: Ultraviolet detection. It allows in a visual way to verify the markings integrated in the ticket with fluorescent phosphors that can not be seen in daylight and are only visible with an ultraviolet light at a certain frequency.
2. IR: Infrared light detection: Other systemOf safety implemented in the tickets is their ink, since under a type of infrared light they exhibit a special behavior. There are two types of ink, the ink that shines when exposed to an IR light and the ink that does the opposite and absorbs the light giving a black tone.
3. MG1 and MG2: This is the magnetic detection. The tickets incorporate a magnetic security system, which is based on a band usually on the sideOf the note, of a ferromagnetic material. This security system is not visible without the proper detector. Another safety system based on magnetic detection is to print the bill with areas of magnetic ink.
4. SIZE: It is based on the detection of the ticket checking its size in length and width. Each ticket has some special characteristics and very specific in terms of measurement, each one of them is fabriTo the millimeter.
5. DD: Thickness detection. Just as each ticket has an exact size, they also have a specific thickness.