DVR & NVR Recorders: specifications, types

The type primarily determines the type of cameras with which the recorder is compatible.

— Analog DVR. Devices of this type can only work with traditional surveillance cameras that output video in analog format (usually via a BNC interface, see below). Despite the emergence of more advanced options, such cameras are still very popular due to their simplicity, low cost and reliability of video transmission. The recorder itself may have a LAN network interface and work as a network device, but it is not compatible with IP cameras.

— Digital NVR. NVR type recorders are designed to work with IP cameras connected via a local computer network. These cameras are more advanced than traditional analog cameras and support more advanced features. The main disadvantage of NVR is the rather high load on network equipment when transmitting streaming video; this can lead to interference and failures, especially when there is a large flow of other traffic on the network.

— Hybrid HVR (HDVR). Hybrid devices that combine DVR and NVR capabilities and can work with both analog and IP cameras. This expands the possibilities for building surveillance networks, allowing you to combine the advantages of both types of cameras and mutually compensate for the shortcomings. However, such equipment is not cheap.

Possibilities for connecting cameras available in the registrar.

For analogue DVRs and digital NVRs (see "Type") in this case, everything is simple: the number of video channels corresponds to the largest number of incoming video signals that can be connected to the device. Such a signal can come both from a camera and from an intermediate device — for example, a quad that combines a picture from 4 cameras. But in hybrid HVRs, the meaning of this paragraph is more specific. For these recorders, this specifies the maximum number of inputs that the device can handle in AHD only mode (i.e., analogue cameras only, no IP cameras). Data on hybrid mode (AHD+IP), as well as for using only IP cameras, are given separately for such recorders (see below).

Numerous channels ( 32 channels, 64 channels and even 128 channels) allows you to create an extensive video surveillance system based on the registrar without using additional equipment (for example, the same quads). On the other hand, this characteristic significantly affects the price, and for living conditions, registrars for 4, 8 or 16 cameras are quite enough.

The number of cameras supported by the recorder when operating in hybrid mode — that is, when using traditional (AHD) and network IP cameras at the same time. For details about hybrid recorders, see "Type". And in this paragraph, the first number indicates the number of conventional cameras, the second — IP devices: for example, the entry "4 + 2" indicates that this model can simultaneously receive a signal from 4 conventional and 2 IP cameras.

Also note that some hybrid recorders allow different ratios between the number of cameras of different types (with the same total number of cameras). For example, a 12-channel model may have 6+6, 8+4, and 10+2 hybrid modes. In such cases, this paragraph takes into account the mode with the largest number of AHD cameras; for the model described in our example, “10+2” will be written in this paragraph.

It is also worth mentioning that when working only with IP cameras, the hybrid recorder can support a greater number of video channels than in hybrid mode — for example, in the “2 + 8” format model, the number of supported only network cameras can reach 16. This information is specified in "IP Only".

The number of cameras (video channels) supported by the hybrid recorder (see "Type") when working with IP cameras only.

Most often, this number corresponds to the total number of channels available in hybrid mode (when IP cameras are combined with traditional, so-called AHD cameras). For example, for a DVR with 8+2 hybrid mode (10 in total), the number of cameras in IP only mode is also usually 10. However, there are exceptions: some models in pure network mode are able to work with more cameras than in hybrid. For example, the same hybrid format "8 + 2" can be combined with support for 16 or even 24 network cameras at the same time.

— PTZ support. Compatibility of the recorder with cameras that have the PTZ function — “pan, tilt, zoom”, that is, the ability to rotate and tilt the lens, as well as zoom in / out. PTZ support allows you to control these functions through the DVR. In analogue cameras, the RS-485 port is used for its operation (see "Additional connectors").

— Responding to movement. A function that allows the DVR to recognize movement in the frame. Specific ways of using this function can be different: automatic start of recording, setting a timestamp (if the video is being recorded continuously), signaling an alarm output, notifying the operator, etc. Note that motion sensors can also be installed in the surveillance cameras themselves; however, the presence of this function in the recorder eliminates the need to specifically look for such cameras (which usually cost a lot).

— Face recognition. This term refers to the extended possibilities for working with the faces of people caught in the frame. Recorders with this function, usually, are able not only to determine the presence of a face in the frame, but to recognize its characteristic features, save the resulting “portraits” and compare them with the database stored in memory. The latter, in turn, allows you to identify people and opens up a number of additional features. A specific set of such features should b...e specified separately, here we will give a few examples. So, in many models, the face recognition system allows you to quickly search for a person in the video archive, eliminating the need for the user to personally view large volumes of video materials. Using such a system, you can record the time of arrival and departure of employees to work, as well as automatically save information about the visits of third-party visitors. Facial recognition can be added to the lock on key cards — and an attacker will not be able to open such a lock, even if he takes possession of the card. There are also more complex and advanced features — for example, the creation of groups of employees with different access rights, with access restriction and/or an alarm when an outsider appears in a prohibited area for him.

— PoC power. An analogue of the PoE technology described above, used in traditional surveillance cameras (so-called AHD). Allows you to supply power to such a camera from the registrar through the same coaxial cable that is used to transmit the video signal; this greatly simplifies the connection and increases the reliability and security of the entire system. So, when installing the camera, it is enough to lay only one wire, while its operation does not require accumulators / batteries, which can sit down at the most inopportune moment.

— Wi-Fi. In registrars, the built-in Wi-Fi module is most often used for two tasks: to work with IP cameras that support such communication, and to connect the registrar itself to a local network (or even the Internet) via a wireless router / access point. And in models with a mobile application (see below), Wi-Fi can also be used for direct communication with the control gadget. Anyway, such a connection allows you to do without fuss with wires and connectors. The disadvantages of this feature include perhaps a slight increase in price compared to analogues without Wi-Fi, but this moment often turns out to be almost invisible against the background of the total cost of the registrars themselves.
Also, the specific supported communication standard can be specified in the characteristics — usually Wi-Fi 4 (802.11n) or Wi-Fi 5 (802.11ac). In this case, the differences between them are most often not fundamental: modern Wi-Fi modules, usually, support several standards at once, so there are no problems with compatibility, and the connection speed is usually more than sufficient to work as intended.

— Wi-Fi ready. This marking means that the recorder does not have a built-in Wi-Fi module (see above), but can use such a connection when an external adapter is connected (usually not included in the standard package). Theoretically, this configuration should provide additional convenience: the user can choose whether he needs Wi-Fi functionality in this particular registrar, and if in doubt, you can purchase the device itself without overpaying for wireless capabilities, and buy the adapter later if necessary . However, in fact, Wi-Fi ready models are extremely rare these days: most buyers decide whether they need wireless when planning their surveillance system, and built-in Wi-Fi modules are not that expensive, especially compared to the total cost of recorders.

— Mobile app. The ability to work with the registrar through a mobile application installed on a smartphone, tablet or other similar gadget. In this case, specific formats for connecting to a controlling gadget can be different: direct connection via Wi-Fi, work via a local network, or even remote access via the Internet from anywhere in the world; Often multiple options are supported. All these details should be specified separately, as well as the specific functionality of the mobile application. However, usually, this functionality is quite extensive, it provides access, if not to all, then at least to the most important functions of the registrar. So, from a smartphone / tablet, you can view footage and live broadcasts from cameras, copy (and sometimes delete) recordings, change many settings, etc. Control applications are usually released for both iOS and Android, so they can be install on almost any modern consumer-grade mobile gadget.

— Support for USB modems. The ability to use an external modem connected via USB to transfer data using the 3G or 4G mobile standard. This gives independence from wires and allows the registrar to be used even where there are no wired computer networks — of course, if there is coverage. Models with this feature usually have wired interfaces, and support for a 3G / 4G modem plays the role of a failover — a backup option in case of problems with the main connection. Note that the specific type of supported mobile network depends mainly on the modem used (the compatibility of the recorder with different models will not hurt to clarify separately, but most often this is not a problem).

— Remote control. The presence of a remote control in the delivery set of the registrar. It is often more convenient to control the device from the remote control than from a computer over the network or from your own control panel.

Compatibility of the registrar with one or another cloud data storage. This paragraph may indicate the very fact of compatibility or specify the specific service for which the device is designed — usually it is Google Drive or Dropbox.

Recall that cloud storage is an information storage system located on remote servers. Data is transmitted to such a system via the Internet, and the owner can also access them via the World Wide Web, regardless of their own location. In addition, modern "clouds" allow you to share selected information with other users. The basic functionality of such services and a certain amount of disk space are usually available for free, but for advanced features and increased storage, payment is required (one-time or regular subscription, depending on the specific service).

Specifically, in this case, compatibility with cloud storage means, first of all, that the recorder is able to directly copy recorded video materials to such storage. This provides two important advantages at once. The first has already been mentioned — the ability to work with videos (view, copy, share, etc.) from almost anywhere in the world where there is access to the Internet. The second point is additional reliability and security: even if the registrar's drive is damaged or destroyed, a copy of its contents will still remain in the "cloud".

Note that support for cloud storage is also found in individual surveill...ance cameras. However, buying a recorder with this function is a more rational solution. Firstly, the ability to work with the "cloud" will not depend on the features of the cameras used; secondly, the corresponding tools in registrars are often more extensive than in cameras.

The number of BNC inputs provided in the design of the registrar.

BNC — connector with bayonet fixation for coaxial cable, used including for transmission of analogue video signal in professional equipment. In registrars, inputs with such connectors are used to connect analogue cameras. The more connectors, the more analogue cameras can be connected directly to the registrar at the same time; and in DVR devices (see "Type"), the number of BNC inputs corresponds to the number of channels.

The number of BNC outputs provided in the design of the registrar.

BNC — connector with bayonet fixation for coaxial cable, used including for transmission of analogue video signal in professional equipment. Outputs with such connectors are designed to transmit a video signal to other components of the surveillance system — for example, monitors.

BNC outputs are found in all types of modern recorders (see above). At the same time, in DVR-type devices, their number, usually, corresponds to the number of BNC inputs, which makes it possible to switch the signal from each camera through its own output. In the NVR, most often only one connector is installed, which is intended for viewing recorded materials, and not images from cameras. The same option is also popular in HVR, although there are also models similar to DVR among them.

The number of RCA analogue audio inputs provided in the design of the registrar.

Inputs of this type are used to connect the audio signal from analogue cameras capable of capturing sound, as well as from separately made microphones. At the same time, the number of such inputs can correspond to the number of BNC video inputs, which allows each analogue camera to be supplemented with sound. However, there are models that have only one RCA input with several BNC inputs.

The number of RCA analogue audio outputs provided in the design of the registrar.

This type of output is used primarily for audio output when viewing footage, in addition to the BNC and/or VGA output. Therefore, there are few such connectors in modern registrars — one, less often two (one each for BNC and VGA).

The number of USB 2.0 ports provided in the design of the registrar. USB is a universal interface for connecting various peripheral devices. In the case of registrars, we are most often talking about "flash drives" and other external media that can be used to copy files or update firmware. However, compatibility with other devices, such as manipulators (keyboards or mice), may also be provided.

Specifically, USB 2.0 allows you to transfer data at speeds up to 480 Mbps and provides a relatively low power supply. Because of this, this version is generally considered obsolete and is gradually being replaced by more advanced standards (primarily USB 3.2 gen1 - see the corresponding paragraph). However, USB 2.0 connectors are still very popular in registrars.

The number of USB 3.2 gen1 ports in the design of the registrar. This interface is used to connect various peripheral devices: USB drives for copying files or updating firmware, keyboards, mice, etc.

Specifically, USB 3.2 gen1 is the successor to USB 2.0. It supports higher data transfer (up to 4.8Gbps) and higher power supply.

The number of HDMI outputs provided in the design of the registrar.

HDMI is the most popular of today's digital interfaces for high-definition video and multi-channel audio. An HDMI input is available in almost every modern TV, monitor, media centre, etc. The HDMI output in the recorders is mainly used to view the captured video; moreover, there is usually less than one such output, since usually, it is not required to connect several external devices at once in this way.

Maximum HDMI resolution.

The maximum image resolution that can be output via HDMI to the screen of the connected video equipment (monitor, TV, etc.). The HDMI output on the DVR allows you to stream Full HD, 2K or 4K images for high quality multi-screen images.

The number of VGA outputs provided in the design of the registrar.

VGA is an analogue video connector originally developed for CRT monitors. It is considered obsolete, but is still quite common in TVs and PC monitors. In registrars, it is mainly used to view footage, so there is rarely more than one VGA port.

The total number of LAN ports (RJ-45) provided in the design of the registrar for connecting to an external network.

LAN (RJ-45) is a standard computer network connector. In this case, they can be found both in traditional DVRs that work only with analog cameras, and in NVRs and HVRs. As a rule, the registrar is equipped with one port of this type, however, there are exception models with two or more ports.

Note that many NVRs are supplemented with RJ-45 connectors for connecting cameras and powering them using PoE. Since these ports are not intended for connection of the registrar with an external network, in this case they are not taken into account, but are indicated separately (see the corresponding paragraph).

The maximum data transfer rate supported by the DVR's LAN ports.

Note that for simple tasks, a rather modest by modern standards speed of 100 Mbps is often enough. However, high bandwidth ( 1 Gbps) not only simplifies the transfer of large amounts of data, but also helps to reduce lags and improve the overall quality of communication; and modern technologies make it possible to provide support for gigabit LAN even in fairly simple and inexpensive registrars.

Of course, in order to use all the features of the LAN, it is necessary that the devices connected to such ports also support the appropriate speeds.

The number of alarm inputs provided in the design of the registrar.

Alarm inputs allow the recorder to respond to various events and signals from other elements of the security system. For example, a door opening sensor can be connected to such an input, and upon a signal from it, the registrar will turn on the camera above this door. This ensures the automation of the security system and makes it less dependent on the human factor.

The number of alarm outputs provided in the design of the registrar.

Alarm outputs are used to transmit signals from the recorder to other elements of the security system — an alarm siren, electronic locks, spotlights, etc. Thus, the system can automatically respond to events recorded by the registrar — for example, block the doors when moving in the frame.

A physical interface for managing and monitoring various aspects of a video surveillance system. As a rule, the RS-485 connector is used in recorders to control PTZ cameras, connect keyboards, matrix switchers and other similar equipment.

The presence of an RS-232 service interface in the recorder (also known as a COM port). Through such a connector, it is usually possible to remotely control the device’s operating parameters from a computer or specialized equipment using appropriate software. Also, the RS-232 port can be used to update the recorder firmware.

Additional connectors provided in the design of the registrar in addition to those described above. Here are the most common types of such connectors:

— RS-232. Service port, most often used to connect the recorder to a computer and manage settings through special software. Technically, it can also be used to control PTZ cameras (see "Design"), but in fact this option is almost never used.

— RS-485. An interface used by PTZ-enabled recorders to send control signals to PTZ cameras. RS-485 is convenient because the cameras can be connected in series and connected to the recorder with one wire (instead of pulling a cable from each camera), while the maximum length of such a wire is 1200 m (without special repeaters).

The maximum data stream in Mbit/s that the NVR is capable of processing when recording and displaying. The throughput parameter is specified as the maximum incoming/outgoing speed, or as the sum of incoming and outgoing streams (total throughput). It is calculated in such a way that the throughput exceeds the total flow of all IP cameras connected to the DVR, and another 25–30% is put in reserve for playing video or viewing it via network access.

The highest resolution in which the recorder can record video when a signal is received from all channels simultaneously. If cameras are not connected to some channels, the recording resolution may be higher (see “Maximum Resolution”).

Higher resolution has a positive effect on detail, but takes up more space and requires more computing power for processing, which accordingly affects the price of the registrar.

The highest frame rate in the recorded video that the recorder can support when recording from all available channels simultaneously. If not all channels are occupied by cameras, this figure may be higher.

The minimum required for comfortable viewing is 24 fps. And in the most modern video standards, the frame rate can be much higher — 50 – 60 fps. Higher values result in better quality and smoother video that allows you to clearly see fast movement; however, such video takes up more space and requires powerful hardware, which affects the price of recorders.

The highest resolution in which the recorder can record video with a frame rate of at least 25/30 fps when a signal is received from all channels simultaneously. The parameter is specified for models that have high resolution shooting with a low frame rate (for example, 4K at 15 fps). It gives an understanding of the specific resolution at which video recording with a frame rate of 25/30 fps is achieved, at which the picture is perceived more smoothly and details in dynamic scenes are better visible (if there are moving objects in the frame).

Standards (codecs) used by the recorder to compress the recorded video.

This parameter is important when viewing recorded materials on another device — for example, a media centre, into which a "flash drive" with files from the recorder is inserted. For normal viewing, it is necessary that the player supports the appropriate codec — otherwise the video will be displayed with distortion or will not work at all. Technical details on various standards can be found in special sources.

Note that if you plan to view the materials on a computer, you can not pay much attention to this parameter: most modern operating systems have extensive built-in sets of codecs, and if you don’t have the right codec, you can easily find it on the Internet.

The maximum supported resolution of IP cameras with which the NVR is technically capable of working (primarily recording). With rare exceptions, devices record in maximum resolution from all connected IP cameras. However, the limiting factor here is bandwidth (see the relevant paragraph) – depending on the shooting conditions, it may not be enough.

High resolution allows you to get a more detailed image in which fine details are better visible. On the other hand, such videos take up large amounts of disk space, and their support significantly affects the cost of the device.

The maximum video recording resolution supported by the recorder when operating in analog mode. If this figure is higher than the resolution when recording from all channels at once (see above), then the recorder is capable of recording at maximum resolution only if some of the video channels are not occupied by cameras. In different models, the required number of free channels may also be different. However, there are instances in which the maximum resolution is achievable even at full channel load.

The number of SATA connectors provided in the design of the registrar.

SATA is the most popular modern interface for connecting internal drives. One connector allows you to connect one hard drive (or other internal media), that is, the number of such connectors is, in fact, the largest number of separate drives that can be installed inside the recorder at the same time. Basic versions can be equipped with one SATA connector or two. More advanced ones have 4 SATA connectors, and already models for serious objects have much greater connectivity.

The number of eSATA connectors provided in the design of the registrar.

The eSATA interface is a modification of SATA, but is not compatible with it and is used exclusively for connecting external drives. It provides a fairly high connection speed (up to 2.4 Gbps); in addition, the use of media for this connector leaves free USB ports that may be needed for other peripherals. The presence of several eSATA ports, respectively, allows you to connect several drives at the same time.

The largest total storage capacity with which the recorder is able to work correctly. By default, it is indicated only for internal media with a SATA interface (see above), however, in some models, data is also provided separately for external devices connected via eSATA.

Note that the limit on the total capacity follows from the fact that each individual port has its own limit on the capacity of the drive. In this case, the maximum capacity is distributed equally between the ports. This should be taken into account when choosing drives for the registrar: for example, in a 32 TB model with 8 SATA connectors, the limit for each connector will be 32/8 = 4 TB. This means that installing two internal 8 TB disks in such a registrar will not work, although their total capacity will be less than the maximum.

The PoE (Power over Ethernet) technology itself allows you to transmit not only data, but also energy to power network devices via an Ethernet network cable. And the presence of PoE output(s) makes it possible to power such devices from the network connectors of the recorder. This eliminates the need to lay additional wires or use independent power supplies, which can be especially important for some equipment, such as external IP surveillance cameras. And when using so-called splitters - devices that separate the PoE cable signal into purely network data and supply power - using such outputs you can also power equipment that does not initially support PoE (the main thing is that their power characteristics match the capabilities of the switch).

As for PoE standards, they determine not just the overall power supply, but also compatibility with specific devices: the consumer must support the same standard as the recorder, otherwise normal operation will be impossible. Nowadays, including in switch connectors, you can find two types of such standards - active ( 802.3af, 802.3at, 802.3bt) and passive (one is called that). The main difference between these varieties is that active PoE provides for matching the power source and load in terms of voltage and power; passive PoE does not have such functions, and energy is supplied “as is”, without adjustments. Here is a more detailed description of speci...fic standards:

- 802.3af. The oldest active PoE power format in use today. Provides power output power up to 15 W (at the consumer input - up to 13 W), output voltage 44 - 57 V (input - 37 - 57 V) and power in a pair of supply wires up to 350 mA. Despite its “venerable age”, it still continues to be widely used; so there are still quite a lot of recorders that work only with 802.3af on sale (as of the end of 2021). However, it is worth considering that this standard covers 4 so-called power classes (from 0 to 3), differing in the maximum number of watts at the output and input. So when using 802.3af, it doesn't hurt to make sure that the output power is sufficient for the selected load.

- 802.3af/at. A combination of two standards at once - the 802.3af described above and the newer 802.3at. The latter allows you to supply power up to 30 W to the output (up to 25.5 W at the input of the powered device), uses a voltage of 50 - 57 V (42.5 - 57 V at the input), while the power in a pair of wires does not exceed 600 mA. This combination is relatively inexpensive, but it makes it possible to power a wide variety of external devices; so at the end of 2021, it is this type of PoE output that is most popular among recorders.

— 802.3af/at, bt. A combination of 802.3af/at described above with the 802.3bt standard (PoE++, PoE type 3 or type 4). 802.3bt is the newest of the PoE power formats; Unlike earlier ones, it uses not 2, but 4 power wires, which allows you to supply very significant power to external devices - up to 71 V (with 90 W at the power output). Such capabilities can be indispensable when supplying energy to equipment with high consumption - for example, external surveillance cameras, supplemented by heating systems. On the other hand, support for the 802.3bt standard significantly affects the cost of the recorder, and such a connection places special demands on the quality of the cables. In addition, you need to keep in mind that this standard also includes the UPoE format, created by Cisco and used in its equipment; and this standard (it is known as PoE type 3) has a more modest power - up to 60 W at the output (up to 51 W at the consumer input). And the general 802.3bt standard includes two power classes - class 8, in which maximum performance is achieved, and class 7, where 75 W is supplied to the output and about 62 W reaches the consumer. So if you plan to use 802.3bt equipment, when choosing a recorder from this category, you must make sure that the power supply is sufficient for the normal operation of the connected devices.

- Passive. As already mentioned, the key difference between passive PoE and the active standards described above is that in this case the power output produces a strictly fixed power, without any automatic adjustments or adjustments for a specific device. The main advantage of this standard is its low cost: its implementation is much cheaper than active PoE, so such ports can be found even in entry-level recorders. On the other hand, the aforementioned lack of auto-tuning makes it much more difficult to coordinate equipment with each other - especially in light of the fact that different devices can differ significantly in the output/consumed voltage and power (power). Because of this, when using passive PoE, you need to pay special attention to the compatibility of the source and load in these parameters. If there is no match, then in the best case (if the voltage/power at the output is lower than required) the power simply will not work, and in the worst case (if there is excess voltage/power) there is a high probability of overloads, overheating and even breakdowns with fires - and such troubles may not occur immediately, but after quite a considerable time. And you definitely cannot connect devices with active inputs to passive PoE outputs - for the same reasons.

Number of LAN ports (RJ45) with PoE support provided in the recorder design.

These connectors are intended for connecting IP cameras. And PoE technology makes it possible to supply power to such a camera directly via the connection cable, thus dispensing with a separate connection to an outlet and without batteries/accumulators. Of course, to use this technology, the camera connected to a similar port must also use it. Most often, the number of channels corresponds to the number of PoE outputs (this can be 4 outputs, 8 or even 16 ports). But there are always exceptions.

The maximum power that the DVR is capable of delivering per PoE output.

Such outputs are described in detail above; just briefly recall that they are Ethernet network ports, supplemented by the ability to power connected equipment directly over the LAN cable, without additional wires. As for the power of such a supply, it must correspond to the characteristics of the connected equipment; however, the term "compliant" may have different meanings depending on the PoE standard being used (see "PoE (output)").

So, if the registrar and the equipment work according to one of the active standards (802.3af, 802.3at, 802.3bt), the output power of the switch must not be lower than the power consumption of the connected equipment. At the same time, exceeding the output power is not scary — the described standards provide automatic adjustment, which allows the powered device to receive exactly as much power as needed, without overloading. But if the output is not powerful enough, it is obvious that it simply cannot provide effective work.

In turn, when using passive PoE, the output power of the power supply should ideally match the power consumption of the load as closely as possible. This is due to the fact that in such cases the power output produces a strictly defined power, with little or no matching and adjustment. And if the excess of a couple of watts, most powered devices are able to transfer more or less "calmly", then a more significant exces...s is fraught with overloads, overheating and equipment failure.

In conclusion, it should be said that if there are several PoE ports and they are used simultaneously, the available power supply per port can be noticeably less than when PoE is operating in only one connector. This point can be clarified by information on the total PoE power (see below) — this power is divided into all the ports involved. For example, if the switch has three PoE outputs, and the power per output is 60 W, then the total power can also be claimed at 60 W. Accordingly, when using PoE on all three outputs at once, the power on each of them will be less than 60/3 = 20 W. Technically, more advanced methods of power management are also possible — with "smart" power distribution depending on the needs of specific devices (relatively speaking, 30 W, 20 W and 10 W for the same total value of 60 W); but for a full guarantee, it is worth proceeding from the fact that all energy is divided equally.

The total power that the NVR is capable of delivering to all PoE outputs.

See above for details on such exits; here we only recall that the general idea of PoE is to supply power over the same Ethernet cable that transmits data. The total power is given for models in which there are more than one such connectors; it allows you to estimate the total power consumption of all PoE devices that can be connected to the NVR at the same time.

There are two important things to keep in mind when choosing a specific value. First, when multiple ports operate, the energy is usually shared equally among them; at the same time, the total power of the registrar does not always correspond to the sum of the maximum powers of all PoE outputs. For example, a model with 8 ports of 30 W each may have a total figure of not 240 W (8 * 30 W), but only 100 W. In fact, this discrepancy means that with the simultaneous use of all connectors, each of them will be able to deliver not 30 W, but a maximum of 100/8 = 12.5 W. The second point is that the total power consumption of the load should ideally be no higher than 75% of the claimed total PoE power — this provides an additional guarantee in case of malfunctions.

The standard supply voltage of the recorder.

It is worth considering that almost all modern recorders are designed for direct connection to an outlet (110 - 240 V). This paragraph also indicates the voltage at the input of the device itself. That is, if the specifications indicate a value less - for example, 12 V or 24 V - this means that the recorder uses an external power supply (which is usually included in the kit). But models for 100 - 240 V use a built-in power supply.

The range of ambient air temperatures at which the recorder is guaranteed to remain fully operational, and the likelihood of interference and failures is minimal. In most cases, recorders are installed indoors with a quite favorable microclimate, while the operating temperature range is quite extensive — for example, a value of -10 ... +55 °C is not unusual. Therefore, you should pay attention to this indicator only when installing in difficult conditions — for example, in an unheated warehouse or in a production room with elevated temperatures.

The highest relative air humidity at which the recorder is able to operate for an unlimited time without failures and breakdowns.

High air humidity has a negative effect on electronics: moisture can settle on various parts, including current-carrying, cause corrosion, short circuits, etc. This does not happen immediately, short-term work in high humidity may not cause any trouble, but a long stay in such conditions is not recommended. However, in most modern recorders, the permissible humidity is quite high — about 90%; indoors, such conditions are very rare.

Support of the registrar of the ONVIF standard.

This standard describes the protocols for the interaction of various components of a video surveillance system; a registrar that supports it will be fully compatible with other ONVIF equipment, regardless of manufacturer.

Recorder compatibility with CMS tools.

CMS is a set of software designed to manage the recorder from a PC. At the same time, the capabilities of this software include not only work with one device, but also the creation of a single video surveillance system from several registrars — so that control and data output from them is carried out through one computer. Anyway, the use of CMS can greatly simplify the work with the registrar.