Today there are many options when choosing a quality CCTV security system. You can choose to go with a traditional analogue system, HD-SDI, HD-CVI or IP network based security products.
Analog Systems Analog, HD-SDI, and HD-CVI cameras require two wires. One for video transmission and one for power cords to power the camera. You can run cox wire and separate power cords, but most CCTV professionals choose to use Siamese cables. Siamese cable is a manufactured Cox cable that is fitted with a power cord. In cases where your power source may not close to your recording device, the power cord may be disconnected from the cocks.
Network IP systems
IP cameras use digital video transmission over a CAT5 or CAT6 cable. In most cases your video and power will run on and off the camera on the same CAT5 or CAT6 wire, assuming you use a POE (Power over Ethernet) power source, such as a POE injector or POE switch.
Some NVRs have made of POE, but in the most cases it recommends to use an external POE switch such as POE-8MB1G. When using an external POE switch, each of your CAT5 or CAT6 cameras will run directly to a POE switch connected to your local network. Then you are connected to your NVR network and you are all set.
If you are going to power your IP camera to 12v / 24v, you will still running from all your CAT5 or CAT6 cameras to a non-POE switch (usually significantly less expensive than a POE switch). But you will running an additional kit to power each camera Power cords from a source.