How an intercom works: operating principle depending on type

Understanding how an intercom works is quite simple. When you apply the key from the outside, the electromagnetic field blocking the door stops for a short time. A similar situation is observed when pressing a button inside the apartment. The operating principle is the same, but the types of devices are different. Each type is described in detail in the presented article.

Principle of operation

Regardless of the specific type, the operating principle of the intercom is general. The device consists of several elements:

1. Call panel – installed on the entrance door or behind the gate. It consists of a reader, a panel with buttons, and is equipped with a microphone and speaker. If video transmission is provided, a small camera is also installed on the panel.
2. Tube – installed in the apartment. Usually it has 2 buttons - on/off and for opening the door. If the intercom device involves video communication, it is equipped with a monitor.
3. Electronic key-identifier – a device with a personal access code. It is read using a key fob (key) and a magnetic card; modern models also provide for the use of biometric data.
4. Electric or electromechanical lock. The first one is more durable, but there is a risk that the door will not open if the power goes out. Therefore, it is better to choose the second option.
5. A cable for connecting all elements (some types of intercoms require communication via a local Internet network or Wi-Fi).
6. The intercom door closer is a typical hydraulic device that performs smooth closing. Works in any weather without freezing, thanks to the addition of special oil.
7. The intercoms are also equipped with auxiliary components - mounting brackets, canopies that protect against precipitation, a power supply and a switch.

Types of intercoms

When choosing a suitable device, you need to understand how the intercom works, as well as what types it comes in. The main classification criteria are related to the type of signal, the number of subscribers and other parameters.

Signal type

For the consumer, this is the most important characteristic. An intercom system in an apartment building usually involves only audio communication with someone who is trying to enter the entrance. But there are also models equipped with a video camera. Thus, according to the type of signal, the models are divided into 2 types:

1. Audio intercoms are the most common option due to their affordable installation and maintenance costs.
2. Video intercoms are equipped with a camera at the entrance and a monitor in the house. Thanks to this, the guest can not only be heard, but also seen. Such models are more expensive, so they are less common.

Signal transmission technology

What the intercom consists of and how it functions depends on the type of signal transmission:

1. Analog - it is transmitted, as in a regular telephone, via cable. To do this, install a small analog switch, which serves as an analogue of a telephone exchange, as well as a multi-core cable leading to each specific apartment.
2. Digital – only 2 cables can be used, while each user is unmistakably identified using a coding system.

There are also wireless systems in which the signal is transmitted via an Internet cable (it is installed separately) or Wi-Fi. These are modern devices that are usually installed in small houses.

By tube availability

There are 2 types of models:

• with a tube - traditional option;
• without a handset (“hands free”).

The principle of operation of the intercom at the entrance is the same, but it differs in terms of the presence or absence of a handset. Most often, there is one - when a call comes in, they pick up the phone and communicate with the visitor through it, just like on the phone.

This is a simple budget option that is most common. But there is also an intercom system without a handset. It provides silence and has a stylish design. It is a panel with a speaker through which you can talk to the guest.

By number of subscribers

According to this criterion, models are divided into 2 types:

1. Individual.
2. Multi-subscriber.

The first ones are installed in private houses, as well as in cottages or 2-3-story houses. They can serve between 10-20 users. In urban high-rise buildings, a multi-subscriber ringing device is used, intended for several dozen or even hundreds of users.

By lock type

Finally, there is a classification depending on the type of lock:

1. Electrical (electromagnetic, magnetic).
2. Electromechanical.

In the first case, the door is blocked by a mechanical unit, which is controlled by an electric drive. In the second case, the door operates entirely using an electromagnetic field, which stops when the key is applied.It is quite obvious why an intercom is needed - it performs the function of not only transmitting a signal, but also opening/closing the door.

It is clear how the video intercom calling panel works. It allows you to enter the apartment either using an electromagnetic key from outside or by pressing a button inside the apartment itself. From a price point of view, it is easier to install a typical audio intercom. But in terms of practicality, it is better to purchase a model with a video camera. In this case, you need to pay attention to the quality of shooting and the reliability of the case so that the outdoor part of the mechanism can work in any weather.