Closed circuit television, or CCTV (stands for closed circuit television) surveillance is a technology designed to monitor a variety of environments and activities. It is called closed, that, contrary to what happens with the media, all components are linked. In addition, unlike conventional television, this is a security system designed to

VDC would be the abbreviation for Volt Direct Current which translated would volts direct current. The idea of ??this type is unidirectional current to the load. Direct current is normally produced by batteries, thermocouples, solar cells and a dynamo electric machine type. The direct current can flow in conductors such as wires, but may also flow through semiconductors, insulators ... In the image: 1 - current per pulse 2 - Direct Current (DC) 3 - Alternating Current (AC) 4 - Variable Current