POE（Power over Ethernet）

Principle

POE is a technology that can transmit data and power through Ethernet cables (Cat5, Cat5e, Cat6, etc.). It uses some of the four pairs of twisted pairs to transmit DC power, while using other pairs to transmit data. The POE standard defines the power supply equipment (PSE) and the powered device (PD). The PSE is usually a POE switch or a POE injector, and the PD is a device that needs power such as an IP camera, a wireless access point, etc.

There are two main versions of the POE standard:

-IEEE 802.3af: Provides a maximum of 15.4W of power, with the actual power delivered to the device being approximately 12.95W, suitable for devices with lower power requirements.

-IEEE 802.3at (POE+): Provides a maximum of 25.5W of power, with the actual power delivered to the device being approximately 21.9W, suitable for devices with higher power requirements.

Advantages

  1. Simplified wiring: Only one Ethernet cable is needed to achieve data and power transmission, reducing wiring complexity and cost.
  2. Flexibility: Allows remote devices to be installed in places where it is difficult to access power, improving the flexibility of equipment layout.
  3. Centralized management: The POE switch can centrally manage and monitor power supply equipment for easy maintenance.
  4. High safety: POE equipment has overload protection, short circuit protection and other functions to ensure the safety of equipment and personnel.

Disadvantages

  1. Distance limitation: The transmission distance of a standard Ethernet cable generally does not exceed 100 meters. A repeater or POE extender is required to exceed this distance.
  2. Power limitation: POE has limited power supply capacity and is not suitable for high-power equipment.

Practical example

For example, to install an IP surveillance system, only one Ethernet cable needs to be laid at each camera location, and power and data transmission are carried out through a POE switch, which simplifies construction and maintenance.

POC（Power over Coaxial）

Principle

POC is a technology that transmits power and video signals simultaneously through coaxial cables (such as RG59, RG6, etc.). While transmitting video signals, coaxial cables can also transmit DC current to supply terminal devices such as cameras. POC technology is usually used to simulate camera systems or transform old coaxial cable systems to support new camera equipment.

Advantages

  1. Utilize existing wiring: The existing coaxial cable network can be utilized without rewiring, saving costs and time.
  2. Long-distance transmission: Coaxial cable can achieve longer distance transmission, usually up to 300 meters or even farther, suitable for large-scale monitoring systems.
  3. High bandwidth: Coaxial cable has high bandwidth capacity and can support high-definition video transmission.

Disadvantages

  1. Poor flexibility: Coaxial cable is thicker and less flexible to bend, and the wiring flexibility is not as good as Ethernet cable.
  2. Equipment compatibility issues: POC is mainly used for specific brands and models of equipment, and there may be compatibility issues.
  3. High wiring complexity: The connectors of coaxial cables (such as BNC connectors) are relatively complex, and wiring and maintenance are difficult.

Practical example

For an old analog monitoring system, when upgrading to a high-definition digital system, POC technology can be used to use the original coaxial cable to achieve high-definition monitoring upgrades without changing the wiring.

Illustration:

  1. POE system framework diagram

 

  1. POC system framework diagram

 

Conclusion

POE and POC each have their own unique advantages and applicable scenarios. POE is suitable for new networks that require flexible wiring, while POC is an ideal choice when you need to upgrade the old coaxial cable system. The specific choice of technology should be based on actual needs, wiring environment, equipment compatibility and other factors.