Diyafon

Intercom is a low-voltage internal communication system used to enable voice communication between two points within a building. Intercom systems typically operate on a “push-to-talk, release-to-listen” principle, allowing occupants within a building to communicate with each other or with visitors at the main entrance. The intercom is a weak-current installation component that directly fulfills communication needs and accelerates contact. Communication is initiated by the user pressing a button on the intercom unit, and the voice from the other side is heard through a speaker.

Applications

Intercom systems are used in various types of buildings and functions to facilitate internal communication. They enable rapid and direct voice communication between apartments and the building entrance in residential complexes, between units in workplaces, between medical staff and support personnel in hospitals, between managers and secretaries in offices, and between teachers and administration in schools. They are also commonly installed in areas with high human traffic such as metro stations, underpasses, and tea houses.

Intercom systems also serve a security function. In particular, in apartment buildings, they allow the identity of visitors to be verified by voice before they are granted entry. In this way, they contribute to access control while simultaneously facilitating communication.

System Components and Building Elements

The fundamental components of an intercom system include the central intercom unit, branch intercom units, external door communication panel, bell button panel, central switchboard (if present), audio or video monitors, and the cables that provide the electrical connections for the system.

For the system to function, at least one communication unit (branch) must be connected to each unit. The central unit has the ability to communicate individually with each branch. The operator at the central unit can initiate communication by calling a branch, or a branch can call the central unit using an audio alert. The connection between the branch and the central unit is established via two-wire or multi-wire systems. Two-wire systems are generally preferred for simple applications, while multi-wire systems are favored in structures serving a larger number of users.

The buttons used in intercom systems are switches that enable users to initiate communication. Pressing these buttons activates the system and starts the conversation. The speaker and microphone are the components responsible for transmitting and receiving audio signals. The external door panel typically includes bell buttons and a speaker. In advanced systems, a camera can also be integrated into this panel.

Operating Principle

The operation of an intercom system is based on the transmission of electrical signals. The user’s voice is converted into an electrical signal by the microphone and transmitted to the other end via the system’s wiring. This signal is then converted back into an audible sound by the speaker in the receiving unit. The “push-to-talk, release-to-listen” operation allows only one-way communication at a time. That is, when one user is speaking, the other listens, and then roles are reversed.

Once a conversation in an intercom system is completed, the system automatically shuts down and becomes ready for a new call. This automatic shutdown duration typically ranges between 10 and 15 seconds. The system is designed to permit communication only between the relevant branch and the central unit, preventing other branches from eavesdropping.

Installation and Mounting Features

The installation of intercom systems is carried out in accordance with weak-current installation regulations. The cables used are low-current capacity, generally shielded, and multi-core. The DT-8 type intercom cable is one of the most commonly used cable types. The diameter of conduits used in the system is determined according to the number of branches and should generally be at least 14 mm. In conduit installations, the junction box is positioned at a height of approximately 150 cm from the floor.

Cable ends should not be excessively stripped during connections, and connections must be made according to the color codes specified in the wiring diagram. Two separate lines are required to connect each branch to the central unit. These connections are made to the terminals indicated inside the central switchboard box.

Components used in intercom systems (terminals, cable lugs, connection screws, etc.) must be manufactured from materials resistant to corrosion and oxidation. The external door panel is typically designed to withstand environmental conditions and may include photoelectric lighting elements.

Types of Intercom Systems and Advanced Applications

Intercom systems are classified into different types according to their applications and features:

1. Audio Intercom System: The most basic type of intercom, providing voice communication only. Commonly used in small apartment buildings and workplaces.
2. Video Intercom System: Allows the user to see the person on the other side. The image from the camera on the external door panel is transmitted to a monitor inside the unit. It can be equipped with infrared LEDs for night vision.
3. Centralized Intercom System: Enables centralized management units in multi-story buildings, hospitals, and schools to communicate audibly with all units.
4. Office-Type Intercom System: Preferred in office and manufacturing environments, this system allows the central unit to call individual branches separately, and branches can also communicate with the central unit.

In advanced video systems, the image of incoming visitors can be recorded along with date and time information via a memory module. This feature enables users to see who visited even when they are not at home.

Electrical Characteristics of the Intercom System

Intercom systems are generally low-voltage systems operating at 12 V. Specialized doorbell transformers or weak-current transformers are used for these systems. The electrical supply is 220 V AC, which is stepped down to low voltage within the system. To ensure clear and noise-free signal transmission, shielded cabling is preferred. The central unit and speaker circuits are configured to ensure smooth and clear audio transmission.

Standards and Technical Specifications

Intercom systems must be designed and installed in accordance with the Turkish Standards Institution (TSE) Internal Installation Regulations and the Ministry of Public Works General Technical Specifications. According to these standards, when one apartment is communicating, other apartments must be prevented from joining the conversation or eavesdropping. The system must operate with a power supply of 180–240 V AC at 50 Hz, and devices must be constructed from materials resistant to mechanical impact. Buttons on the panel must be durable against dislodgement and breakage, and nameplate sections must be enclosed in transparent covers.

Use of Intercoms in Elevators

Intercom systems installed in elevator cabins are designed to establish communication with the outside world in emergency situations. These systems enable passengers trapped inside the cabin to establish direct voice contact with building security, management, or the doorman. The intercom may be handset-based or button-operated. When the button is pressed, an audio alert is triggered at the other end, initiating two-way communication. In some elevators, a telephone handset may be used instead of an intercom. The speakers, as part of the intercom system, can also transmit audio announcements and music within the cabin.

The intercom is a low-voltage, safe, and practical communication system used to provide internal voice communication. With advancing technology, it now offers both audio and video communication capabilities, enhancing security and comfort. As a component of weak-current electrical systems, it is widely used in apartment buildings, workplaces, and public facilities.