Power over Ethernet (PoE) can be used to describe any system that passes electrical power on Ethical cabling along with data. The system may be any standardized or ad-hoc system. In this way, a single cable can be used to provide both the data connection and electrical power. The devices that usually require both, data and electricity are wireless access points or IP cameras.
The best part about the PoE is that it allows long cable lengths. As compared to the USB (Universal Serial Bus) standard, this is better. Power may be carried on the same conductors as the data, or it may be carried on dedicated conductors in the same cable.
As for the POE Injector ; there are many techniques. However, IEEE 802.3 has standardized only two of them. For such a transmission, only two pairs are needed. So, the power is transmitted through the unused conductors of a cable. The power can also be transmitted by using a common—mode voltage. It has to be applied on each pair of the data conductors. But, does it interfere with the data transmission? No, it doesn’t as it uses differential signaling.
What about the common mode voltage? It is extracted using the center tap of the standard Ethernet pulse transformer. This can be compared to the phantom power technique. This technique is used for powering the audio microphones.
And, that is not all that IEEE standards do. It also sets the standards for signaling between the power source equipment (PSE) and powered device (PD). It also standardizes the practices for spare-pair and common-mode data pair power transmission. So, what exactly is done? The conformant device is detected by the power source. This allows the device and source to negotiate the amount and source to negotiate the amount of power required or available. Up to 25 watts is available for a device, depending on the version of the standard in use.
The best part about the PoE is that it allows long cable lengths. As compared to the USB (Universal Serial Bus) standard, this is better. Power may be carried on the same conductors as the data, or it may be carried on dedicated conductors in the same cable.
As for the POE Injector ; there are many techniques. However, IEEE 802.3 has standardized only two of them. For such a transmission, only two pairs are needed. So, the power is transmitted through the unused conductors of a cable. The power can also be transmitted by using a common—mode voltage. It has to be applied on each pair of the data conductors. But, does it interfere with the data transmission? No, it doesn’t as it uses differential signaling.
What about the common mode voltage? It is extracted using the center tap of the standard Ethernet pulse transformer. This can be compared to the phantom power technique. This technique is used for powering the audio microphones.
And, that is not all that IEEE standards do. It also sets the standards for signaling between the power source equipment (PSE) and powered device (PD). It also standardizes the practices for spare-pair and common-mode data pair power transmission. So, what exactly is done? The conformant device is detected by the power source. This allows the device and source to negotiate the amount and source to negotiate the amount of power required or available. Up to 25 watts is available for a device, depending on the version of the standard in use.
