PoE (Power over Ethernet) switch is a switch that uses a technology to transmit data and power over the same wires, using a twisted pair. Switches are required to connect several nodes of a computer network.
This is what a POE switch looks like, it is also called a switch (switch)
Computers are connected using an Ethernet cable to the switch. This device can receive and transmit data, determining its source and destination and transmitting packets of information only to those nodes in the network for which they are intended. For this, switches use switching tables - the scheme of correspondence of the MAC address of the computer in the network to the switch port. The switch just powered on has an empty table. While transmitting data over the network, it analyzes the MAC addresses of the sending device and enters them into a table located in the associative memory. If the device then receives data assigned to a computer whose MAC address is in the table, the switch will send a signal only through the port associated with this node. The advantages of switches are their high speed of operation, in contrast to hubs.
Using switches for video surveillance
Network video surveillance is used to organize video surveillance through the use of computer networks that allow data transmission to anywhere in the world.
Visual signal registration is carried out by means of IP cameras, which transmit digitized data over networks using the IP protocol. Switches provide additional functionality for surveillance systems. Several cameras of a video surveillance system can be connected to a switch, which distributes digital data streams between output devices: computers, video servers, monitors, etc.
The most modern video surveillance systems use controlled switches that have an interface for configuring the behavior of devices depending on the signals coming to them, transmitting information in the event of alarm sensors being triggered to certain network nodes, etc.
PoE technology and video switches
Recently, the technology has become widely used to organize digital video surveillance systems.
PoE benefits:
- Simplification of the electrical system: no large number of power cables extended to all devices.
- Security: PoE switches convert 220V to power the cameras, usually 12V.
- Increase the range to the powered device.
- The ability to turn off / reboot devices in the system remotely.
- Possibility of extensive management of devices on the network.
PoE camcorders can be powered via an Ethernet cable. The switch for video surveillance, connected to the electrical network, converts the alternating current into constant power of the required power. The same function can be performed by a PoE injector connected to a switch or directly to an outlet.
PoE injector circuit
Typical POE injector: connector for power supply, connector for LAN line and signal transmission to the camera, already powered by POE
A typical injector has two ports: a device supporting the technology is connected to the POE, and a computer / switch / router to a LAN.
Scheme for connecting the injector to the system
The figure above shows that one switch, depending on the number of ports, can include several devices powered by Power over Ethernet technology. For equipment that does not support PoE, splitters can be used that convert the Ethernet signal into a digital data stream and an electrical power supply component.
Popular PoE Video Switches Models
Sigrand
The company manufactures products for video surveillance systems: IP cameras, switches (including PoE), PoE floodlights, etc. In the SG-1 series, models have 6 Ethernet ports, give power up to 60 V. The interesting thing about Sigrand's equipment is that that the equipment can be connected in series in one line. This saves money and reduces consumable costs.
Schematic of building a network based on Sigrand equipment
Sigrand POE switch appearance
Building and testing the network before starting installation
Raisecom
The brand provides a wide selection of various equipment and switches that can be used in video surveillance systems. ISCOM series switches feature a large number of ports and the ability to remotely manage.
RAISCOM equipment can be integrated in different ways
Cisco
The company has a large selection of switches that can be used in industry. The devices are compact, energy efficient, programmable. A well thought out API is used for programming. Cisco is a fairly common brand that has high quality industrial equipment in its catalog. The company has a very high quality, and the price, as you know, always depends on this indicator.
There are many different other brands out there that are no worse or better (though, how to look). It is better to make the choice according to technical characteristics, appearance, installation method and location, as well as price. I would also recommend using the reviews.
In the next article, we'll talk about POE injectors: how they differ from POE switches, what are the advantages and disadvantages.
Network switches, also called switches, are used in IP video surveillance, ip cameras are connected to them. They give connections to LAN modules.
A switch is a network device designed to connect, combine multiple hosts into a network.
A PoE switch is a device that allows the transmission of electrical network signals over a twisted pair, along with the data of the network interface. Thus, this technology allows powering IP cameras through a twisted pair.
In operation, the network switch looks at the MAC addresses of all connected devices and collects a port map. You can call it a table. When the device is turned on, its table is empty. Further training begins. See the figure below.
In the figure, we see two columns:
- address;
- interface.
The "Address" column contains the device's MAC address, in our case the camera's address.
The "Interface" column contains the rj45 port number.
Now we know a little how the table of Mas addresses is compiled.
Below we see the diagram for connecting an ip-camera through the POE switch.
Characteristics
Poe switch When designing IP video surveillance, the characteristics of the switch and the conditions of the surveillance performance are matched:
- Bandwidth;
Each switch for monitoring has a certain bandwidth, it can also be called a switching matrix. It can be explained in another way: the amount of traffic that a device can transmit per unit of time. The switching matrix of each switch should be considered.
Most often, the total, passing capacity is lower than the total value of the entire system, in which case the device will work with lags and freeze.
- Number of ports;
A larger number of installed ip-cameras depends on this characteristic.
For small objects, most often switches are used with a small number of ports. In the case of professional video surveillance, devices with 8.16 and 24 ports are used. When choosing the number of ports, you need to consider the bandwidth.
- Execution;
Switches can be both for external surveillance systems and for internal ones. For street systems, they are used in any climate. Internal systems use standard switches.
- PoE availability;
The existence of Power over Ethernet greatly facilitates the installation of IP video surveillance, because the power is supplied over a twisted pair cable. But not all cameras are compatible with PoE, so you need to look in the specifications to see if the camera supports this function.
- Features of switches with Power over Ethernet;
PoE is a function to provide power to a remote supply using an Ethernet cable. With all the difficulty of installing video surveillance systems, power and data transmission have their own cable, which is why experts often prefer equipment with PoE.
- The power of the power supply is an important aspect in choosing a switch, since 25 W PoE is not enough for it.
However, nowadays, they began to produce switches with high power PoE. This innovation makes it possible to use powerful cameras, IR illuminators and other additional equipment. But still, each time you need to carefully calculate the required power and correlate it with the switch reserves.
Switch selection
The choice of a switch must be taken very seriously, as it limits the data transfer rate.
The normal network supply has not been updated with regard to the amount of image sent by the camera. The most common models provide processing of a program up to 1518 bytes. This means that they are adapted to work with powerful IP cameras with high image resolution, and this most often leads to a freeze in the supply.
The main difficulty in buying is technical specifications, which are not always similar to reality. For example, bandwidth is signed by not including all ports in its operation, so in some cases the system refuses to start.
The most important aspect in choosing a switch is the scope of application. For example, in IP surveillance for the home, cheap equipment with the same IP cameras with low image resolution is most often used. In some cases, the system is bypassed by a router instead of a switch, but this is enough only for a couple of cameras.
All commercially available switches are classified into Fast Ethernet and Gigabit Ethernet. A parameter that must be taken into account when choosing. This is the characteristic of the bandwidth: Fast Ethernet - 10/100 Mbps, Gigabit Ethernet - 10/100/1000 Mbps.
Symmetrical and asymmetric switches
Symmetry and asymmetry characterize a network switch in terms of the bandwidth of each port. A symmetric switch connects ports with the same bandwidth — 10 Mbps, 100 Mbps, or 1000 Mbps. An asymmetric switch connects ports with different bandwidths - 10 Mbps with 100 Mbps, 100 Mbps with 1000 Mbps. Such devices are used when there are large network flows "client-server": users simultaneously exchange data with the server, and this requires a wide bandwidth for the port. When streaming from a 100 Mbps port to a 10 Mbps port, the switch uses a memory buffer to avoid congestion. The size of the memory buffer is an important selection criterion.
Unmanaged and Managed PoE Switches
The unmanaged switch is simpler to use — ready to install out of the box with no configuration required. Ideal for typical systems. The managed switch provides fine tuning of many parameters. The devices are designed to solve complex problems, build branched out large systems, including equipment of different technical characteristics. A modern PoE switch is a complete element of a comprehensive security system.
The very name "PoE switch" means that the device performs communication tasks and simultaneously distributes energy. But connecting several nodes to a network and powering devices over twisted pair are far from all functions. PoE switches in functionality are not inferior to network switches, on board:
- Setting the bandwidth of each port.
- Bandwidth reservation for applications.
- Traffic prioritization.
- Static routing.
- Network storm protection.
- Port mirroring.
- Aggregation.
- Supports SSL and SSH encryption.
- Detection of loops in the network with further isolation of the port and cable diagnostics.
- Quantitative limitation of learned mac addresses.
- Access list and the like.
Most of these functions are also present in unmanaged models, but they do not have the ability to customize (it is not always needed - it depends on the tasks).
Voltage
At the output, the PoE switch provides 48 V. The voltage of the powered device is 12 V. This is due to inevitable electrical losses during transmission over long cables. Thus, the required amount of energy reaches the energy consumers, which would not have happened if the output of the switch was 12 V. When the distance between devices is small, losses are minimal. For such a case, each end device is equipped with a converter that adapts the voltage level, and there are switches on sale that operate in several modes.
Number of ports
The number of ports is an ambiguous characteristic. 4-port, 8-port, 16-port, 24-port are common names, not talking about the number of PoE-enabled connectors. When you need to connect 8 CCTV cameras to the switch, you need 8 PoE ports, but in fact there are at least one more ports: in addition to RJ-45 with PoE, there is also Ethernet without PoE support, SFP, combined. When buying a switch, keep in mind that 4 devices need exactly 4 PoE ports, for 16 - 16. 4, 8, 24, 48 is an international standard. 16 ports are a Russian invention. Customer-focused manufacturers produce switches with 2, 5, 6, 7, 9, 10 or more ports with PoE support.
PoE budget
PoE Budget is a characteristic of each port and its aggregate. Please note: the budget for each port separately is higher than the budget for the same port, but at maximum load (using all connectors). Example: 15W port, total 8 ports, total budget 100W. In case of excessive consumption, energy is not supplied to one of the ports - according to the sequence set (manually or provided by the manufacturer). When purchasing a PoE switch, consider your overall PoE budget.
You can buy Netis, Osnovo, TP-Link, Hikvision, Trassir, Hikvision PoE switches from us. Trassir products are ours, the rest are our partners. On sale Netis, Osnovo, TP-Link, Hikvision at manufacturer prices.
What is PoE?
PoE stands for Power over Ethernet.Ethernet). But the implementation of the technology is much more complicated than using a cable with a power plug at one end and an RJ-45 connector at the other, as in the humorous picture at the beginning of the article. Such a simple implementation is simply impossible, since most electronic devices operate not on alternating, but on low voltage direct current: 12V, 24V, 48V, etc. Therefore, the network must have devices that perform, among other things, a step-down transformer and a rectifier.
In a network cable (twisted pair) with a 100BASE-T (Fast Ethernet, 100 Mbps) connection, data is transmitted over only 2 pairs, and the remaining 2 pairs remain free. One day, someone very smart came up with the idea of \u200b\u200busing these free conductors to supply power to devices. The technician receives both data and electricity over a single LAN cable. It is very convenient for those cases when the equipment needs to be installed on the roof, on a mast, in the yard of a private house, that is, in those places where it is problematic or expensive to bring a separate cable with power supply.
Later, another option arose - to supply current through the same veins as the information. This made it possible to apply the technology in Gigabit Ethernet networks, 10/100/1000 Mbit / s, where all 4 pairs are involved in information transfer. Power and data are transmitted at different physical levels, so they do not interfere with each other.
PoE devices
Within the framework of the technology, 3 types of devices are distinguished:
PoE Consumers (PD)
PoE Splitters
Designed for organizing remote power supply in the network if the end device that needs to be powered does not support PoE technology. Splitters act in the opposite direction to PoE adapters: they divide the power supply and data coming to them over one cable (twisted pair) into two cables: separately electricity, separately data.
A PoE splitter can also be structurally a block or a cord.
PoE converters
During the construction of links, a situation may arise when the PoE source and consumer operate with different voltages, different standards. For these cases, there is such a group of devices as PoE converters.
How to use PoE to provide power over a twisted pair cable
Connection options using different types of devices using PoE technology are clearly illustrated by this picture with diagrams:
What is important to know for correct connection
So we bought some kind of PoE adapter, connected it to Ethernet and the mains, connected the LAN cable from it to the access point that we wanted to power. Seems simple.
Power over Ethernet (PoE) is a special technology with which electrical energy is transmitted to power the device along with data via the same cable for communication with an Ethernet network.
Benefits of PoE Power
Thanks to this technology, the user does not need to locate the device in close proximity to the source of electrical energy and lay additional electrical wiring, and therefore significantly expands the area of \u200b\u200bplacement of this device and significantly reduces the cost of installing it. In this way, poE power supply provides a highly ergonomic work environment, taking into account the unloading of the premises from additional adapters and bundles with wires, and is also economically profitable for the customer due to the absence of unscheduled costs associated with the installation of new sources of electricity.
Indeed, in rooms with a large number of multipurpose equipment, it can be very difficult to provide electricity to each of the devices. Mobile devices such as security cameras, personal computers, wireless access points and IP phones require installation in locations that are often remote from power outlets and sometimes require movement. The best solution to this problem is a PoE switch that will provide power to PoE-compatible devices.
Installation Basics
In order to install PoE power from the switch to the desired device, it is necessary to connect a special PoE injector to the switch port and to the power supply at the same time. Often, switches of this type are produced with built-in injectors, which greatly simplifies the installation and configuration of technical equipment connected to these switch ports. The main advantage of the built-in PoE injector is that the switch has several PoE ports at once, and therefore this power supply method becomes possible not for one, but for a number of devices.
DC Power Issue Technology in PoE
It has been argued that DC power provided by PoE power is inherently less efficient than AC power because of the lower voltage. Let's look at this statement. A typical 48-port PoE switch supporting Power over Ethernet technology has a 50W to 80W power supply. In addition, a power supply of 740 W (for the IEEE 802.3af standard) or 1480 W (for the IEEE 802.3at standard) is usually required. exclusively for PoE ports... Initially, using a long cable may seem ineffective. However, where this centralized power supply replaces multiple AC sources at the same time, and also prevents costly human intervention (electrical wiring), power losses due to a long DC cable can be fully justified. Every year manufacturers, guided by the most modern requirements of the high-tech market, create more and more powerful and multifunctional switch models. The leading manufacturing companies are trade marks Cisco and Hewlett & Packard.
