Comparison Dahua DH-VTH5221D vs Dahua DH-VTH1550CH

The total number of ports for wired connection of various equipment provided in the intercom; in fact — the maximum number of wired devices that can be simultaneously connected to the intercom.

Keep in mind that this number may be less than the total amount of supported devices. This is especially true in models with the possibility of using additional monitors (see "Connected monitors"): such devices are often connected in series, "chained" and occupy only 1 port. Thus, for example, an intercom for 2 calling panels and 3 monitors can have only 3 connectors — one for calling panels and one for monitors. Note also that the LAN port in IP intercoms (see "Device type") is also taken into account in this calculation.

The number of outdoor panels that can be connected to the intercom at the same time.

The call panel is an external panel through which the guest sends a call to the owner of the intercom and communicates with him. Such a panel should be at each door "covered" by the intercom. This means that the number of supported outdoor panels corresponds to the maximum number of doors with which this model can be used. The simplest option is 1 calling panel, but in fact this is often not enough. Therefore, models that can block 2 doors at once are more popular — for example, the main and service entrances to the office. And in the most advanced intercoms, it may be possible to connect 4 calling panels at once, or even more.

The number of video cameras that can be simultaneously connected to the intercom. The mode of operation with these cameras can be different — a mosaic of several signals at once, switching between signals with each one displayed on the full screen, etc. However, anyway, to work with several video cameras, it is desirable that their corresponding number be directly claimed in the intercom — otherwise you will have to resort to installing additional equipment.

The simplest modern intercoms allow the connection of 1 or 2 cameras, in more advanced ones this number can reach 4 or more.

— Android OS. The advantages of the Android OS include flexibility, which allows you to install third-party applications, thereby increasing the functionality of the device. Such applications may include SIP phones, programs that allow video surveillance, and others. But it is worth noting that such devices are not very suitable for the role of using a full-fledged tablet; firstly, most have a stationary location, and secondly, as a rule, the power of intercoms is not so high. Also, various restrictions may be set separately by the manufacturer; this must be clarified separately.

— Wi-Fi module. The Wi-Fi wireless communication module is found only in IP intercoms(see “Device type”). This function allows the device to connect to the network wirelessly - this is much more convenient than pulling cables, and the quality of communication is usually indistinguishable from a wired one. Another option for using Wi-Fi is a direct communication to a smartphone or tablet and using such a gadget as a remote control with an external screen; however, such an opportunity is provided relatively rarely.

- Mobile app. This feature means that the device can be operated via a smartphone or tablet with a special application installed on it. Such applications are usually released immediately for both of the most popular mobile operating systems today - Android and iOS; ho...wever, it would not hurt to clarify this point separately. In any case, control from a mobile device can have very extensive functionality (including even the ability to work via the Internet, in some models); and interacting with a device through a gadget that you can always keep with you is definitely more convenient than going to an intercom or other stationary equipment every time.

— SIP protocol. The intercom's support for the SIP protocol allows the intercom to redirect the signal from the calling panel through the telephone network to a mobile device, a stationary PBX or a computer with the appropriate software. Such a function may be useful, for example, in an office where there are a lot of visitors, and going up to the intercom every time to answer is inconvenient. Additional SIP capabilities in different models may vary significantly; they should be clarified separately.

- DVR support. The ability to operate the intercom in video recording mode from calling panels or from separate surveillance cameras. In most of these models, recording is not carried out constantly, but only when the call button is pressed or another event occurs - for example, a motion detector is triggered (see below). Video is most often saved to a memory card (see “Card Reader” below). In any case, this function allows you to find out who called the intercom at “inopportune hours”; it can also be useful in other situations - even to restore the picture of an emergency that came into view of the cameras.

— Internal communication (Intercom). This function allows you to make calls between intercoms on the same network. Depending on the implementation and settings, there is an addressable intercom, when you enter the number (identifier) of the device on the network to which you want to make a call, as well as options for setting up a general call, when the call goes to all devices on the network. In any case, this function will be useful if there are several intercoms in the network, so you can call, for example, a neighbor.

- Speakerphone. A hands-free function similar to that found in telephones. In this mode, a loud speaker and a sensitive microphone are used for conversation, located in the intercom body and allowing you to communicate comfortably at some distance from the device (up to a meter, or even more). This function is especially important for models with a handset (see “Execution”) - it allows you to talk without holding the handset. But devices without a handset, by definition, operate in a hands-free format.

- A voice message. An analogue of the answering machine function in phones, when the subscriber can leave a message if the owner of the intercom does not respond to the call. The function can be implemented in different ways, but in any case it is similar to the one with the usual expression: “Leave your message after the sound signal...”.

— Picture in picture. The ability to display a second image on the intercom screen, in addition to the main image. In this way, you can, for example, check the situation in the visibility range of a surveillance camera without interrupting communication with the visitor via the main video panel. The additional picture is small in size and is usually displayed in one of the corners of the screen.

- Motion Detector. A function that allows the intercom to detect movement in the visibility range of connected cameras and respond to it. The specific method of such a reaction may be different in different models: turning on recording, sending a notification to a user-specified device, sending a signal to an alarm output, etc.; These details should be clarified separately. In any case, the motion detector reduces the likelihood of missing significant events in the field of view of the cameras.

— Built-in memory. Built-in memory is found in video and IP intercoms (see “Device type”) and is usually intended for storing data from surveillance cameras. However, the volume of such memory is usually small, and it is usually used only for photographs (for example, to capture the faces of visitors); Video recording, if provided, is carried out on a memory card (see below). In any case, it would not hurt to clarify the operating features of the built-in memory separately.

- Frame. The ability to operate the intercom in digital photo frame mode - when photographs stored in the device’s memory (or stored on a memory card) are displayed on the screen (usually in slideshow mode). A mandatory feature of models with this function is a fairly large color screen - only on it photos will be normally visible; The intercoms themselves are usually video or IP models. The main purpose of the photo frame mode is aesthetic: showing beautiful pictures, the intercom plays the role of additional decor for the number.

Resolution of the display installed in the intercom.

All other things being equal, a higher resolution provides a smoother and more detailed image, but it does affect the cost of the screen. In addition, all the benefits of high resolution are lost if the camera you are using does not support it. In general, this parameter is secondary: it is selected by the manufacturer based on the screen diagonal and the general functionality of the device, and for many screens it is not indicated at all - it is believed (and quite reasonably) that the resolution is in any case sufficient for its intended use. Therefore, there is no point in chasing a Full HD screen ; an HD display, or even an SD one, will be enough.

The temperature range at which the intercom is able to work normally.

If the device is installed in a residential area or office, you can not pay much attention to this parameter: the temperature in such an environment rarely goes beyond +18 ... +25 °C, such values are normally tolerated by any intercom. But if the device needs to be placed in a "non-standard" microclimate — for example, an unheated warehouse, where conditions do not differ much from outdoor ones, or a production workshop with a high temperature — you should make sure that the chosen model can normally endure such conditions.

Separately, we note that even the most “heat-resistant” intercom cannot be exposed to prolonged exposure to sunlight.