Difference between using PoE and DC as power supply.

What is the difference using between PoE and DC?
What are the pros and cons?
Is it okay to insert both PoE and DC? What are the benefits having both?

(1) POE application scenario: It is used to transmit data and power simultaneously through Ethernet cables. Commonly found in devices such as IP cameras, wireless access points, VoIP phones, etc. that require networking and may be located far from an electrical outlet.
DC application scenario: Provides stable direct current (DC) for the device. Common in all kinds of electronic equipment, such as computers, mobile phone chargers, LED lamps and so on.
(2) POE advantages: simplified installation, flexibility, security
POE disadvantages: high cost, power limitation, heating problems
DC advantages: low cost, wide power range, high efficiency
DC disadvantages: complex wiring, lack of flexibility, decentralized management
(3) Whether you can plug in PoE and DC at the same time: In general, you should not connect a device to PoE and DC power at the same time. Most devices are designed to accept only one mode of power supply, and connections can cause circuit damage. However, some devices do support dual power inputs (PoE + DC), but in this case, there is a mechanism inside the device to ensure that power is not taken from two power sources at the same time, usually choosing PoE power first, and only switching to DC power when PoE is not available.
(4) Benefits of both:
Redundancy: If the PoE power supply fails, the DC power supply can be used as a backup to ensure the continuous operation of the device.
Adaptability: In different environments, the most suitable power supply mode can be selected according to the actual situation.
Scalability: When the network architecture changes or new devices need to be deployed quickly, you can choose the power supply method that best suits the current conditions.