Analog security cameras are almost always powered by either 12V or 24V DC which requires the use of a power adapter. Standard plug in power adapters are an economical choice when there is a power supply close to the camera or when only 1 or 2 analog cameras are being used. When centralizing all camera power to one point (near the DVR), it is best to use a dedicated wall mount power supply which are available in 12V, 24V or combination units. When choosing a power supply, one must ensure that it provides adequate amperage that can accommodate the draw needed by all cameras. Infrared and PTZ cameras require more power than standard cameras. For example: a standard camera can draw up to 250mA and an infrared can draw up to 400mA when it’s emitters are on. If you had three of each, you would need a power supply that could supply at least 2A with 6 terminals.
IP cameras make use of PoE which stands for “Power over Ethernet”, an industry standard for providing low voltage power using CAT5 cable. This standard is becoming increasingly popular primarily for voice over IP (VoIP) and can be found on common switches, hubs and even firewalls. For those with existing network infrastructures, PoE injectors can be used which are small devices that are placed inline with your IP camera. The injector simply passes all data in/out and applies power to your IP camera. For new implementations, PoE switches are available in 4, 8 and even 20 port models available from a variety of vendors such as Cisco, Mobotix and 3COM.
Regardless whether you are implementing an analog or IP video surveillance system, it is best practice to implement a UPS, or Uninterruptible Power Supply. Not only do they provide battery backup power during power outages, they filter sags and spikes – providing clean power for your security camera investment. Implementing a UPS is easier when all power leads are centralized to one point. If you are implementing IP cameras, the PoE switch (or injectors) should be plugged into the UPS. If you are using analog cameras, the power supply should be plugged into the UPS. Plug power adapters into a power bar and plug the power bar into a UPS if you are using the economical route. Security cameras are similar to any other electronic device – they are sensitive to power.