Intercom connection type
Type of connection with additional monitors (see "Number of monitors") supported by the intercom
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Consistent. With this type of connection, all external security devices — calling panels, cameras, locks, etc. — are connected only to the main intercom. Additional monitors used in the system are connected in a "chain", one after another, and work only through the main unit; you cannot connect security equipment directly to an additional monitor. With this format of operation, the number of security devices is limited by the capabilities of the main intercom, but they can be accessed from any system monitor.
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Parallel. Like serial, this option assumes the presence of a main intercom and additional monitors. The key difference lies in the fact that you can connect your own video cameras to each controlled monitor, which will be controlled only from this monitor. This option is convenient when organizing security systems with several separate video surveillance zones: for example, the main monitor can be installed at the main entrance, and the additional monitor at the service entrance, and each of them will only work with the camera above the corresponding door.
Number of ports
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.
Maximum call duration
The longest continuous conversation that the intercom provides. Technically, this duration can be unlimited, but in fact, limits can also be set — usually from 1 to 4 minutes. This is primarily due to the fact that in systems with several call panels, a conversation through one of them may interfere with the work of the others. Limitations on the duration allow you to exclude long conversations and possible overlays, and the available time is usually enough to clarify all the necessary questions during one conversation. Also, this feature is useful in case you forget to turn off the connection (hang up) at the end of the conversation.
Operating temperature
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.
Horizontal viewing angle
The horizontal viewing angle provided by the camera on the entry panel of the intercom.
This parameter has a double meaning: other things being equal, a wider field of view allows you to cover more space, but reduces the size of individual objects in the frame. So it’s worth choosing according to this indicator, taking into account what is more important for you — good visibility on the sides or an additional degree of increase. As for specific values, in modern outdoor panels they can vary from 50° (directional cameras) to 166° (ultra wide-angle lenses with a minimum of dead zones on the sides).
Operating temperature
The range of air temperatures in which the call panel maintains normal performance.
Outdoor panels installed outdoors and in unheated rooms are subject to the greatest temperature fluctuations, therefore, it is with this installation that this parameter should be paid special attention. At the same time, we note that even the most “heat-resistant” models must be protected from sunlight. If the conditions in the room are comfortable for people all year round, then they will be quite normal for the call panel, in such cases you can not look at the operating temperature at all.
