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.

The RJ-11 is mainly used to link telephone networks connector. It is small and has four contacts measures to support 4-way 2 cables. It is the most widely used globally for connecting conventional telephones, which generally tend to use only the two central threads to a single line or a twisted pair connector. And the four wires are used only for telephony equipment special using double line or two telephone pairs. After crimp the cable, it is almost impossible to disarm the RJ-11 without causing its deactivation.