POE injector: designation, description

POE injector is an elementary network device, which greatly facilitates the installation of network instruments in the enterprise or in the office. Power-over-Ethernet (PoE) technology allows the network equipment to be powered by a network cable, thus eliminating the need for the users of this equipment to install electrical outlets in places where this is inconvenient, as well as the use of bulky power supplies.

Let's look at the advantages of such a device as a POE power injector. When installing an Wi-Fi access point, network camera or router in an office, you need to consider where the nearest socket (220 volts) is located to connect the power supplies from the listed equipment. Often this can significantly limit your ability. Very often, in order to get the best level of Wi-Fi signal, you need to place an access point higher, for example, under the ceiling. In this case it is necessary either to lay the wiring and install a new outlet under the ceiling, or to sacrifice the signal quality and install the equipment where the power supply allows. And if you need to install network equipment in hard-to-reach places (on the roof, attic, and so on), then the cost of wiring and installation of outlets can be very high. To solve such a problem, IEEE 802.3AF standard was created, which allows to transmit electric current through the Ethernet network. To ensure the operation of devices it is quite sufficient existing cables of the third or fifth category. Unlike the 220 volt network, where electricity is supplied to all receivers, the POE injector distributes power to each device individually.

Since all computer equipment is powered by direct current, the ROE standard implies the transfer of a twisted pair of direct current over a cable with a voltage in the range from 44 volts to 57 volts. This value was chosen because it can be fed via twisted pair cables without any length limitation. To transfer electric current in the cable, two pairs are allocated, for each of them a current is supplied within 175 milliamperes (total 350 mA). Accordingly, the power of a device such as a POE injector can reach 16 watts. This is more than enough to power the network equipment.

In fact, a POE injector is a device that transmits electrical power to a signal cable . This device can be integrated into network equipment (in routers) or be implemented as a stand-alone device. In the latter case, the POE injector is connected to the section of the twisted pair and to the 220-volt network. The input of this device receives only data, and already at the output - the electrical voltage and data.

In conclusion, we add that the ROE technology was conceived as an opportunity to cut costs when pulling networks in offices and enterprises. However, it quickly gained popularity in the private sector, because it greatly simplifies the connection of network equipment and eliminates a large number of unnecessary power supplies.