How to Design a Building Telephone System

An essential part of building services electrical project is the Telephone System. The telephone system enables building occupants to communicate internally without being charged by the network service providers. They are mainly deployed in almost all types of building projects and a few in the residential project. In addition to using them as individual daily values, it Provides confidentiality for calls in enterprises and managing emergency calls in hospitals.

The telephone systems do not only manage floors and zones within a single building but can also be scaled to manage multiple buildings within an estate, campus, or community.

This post will provide you with the working knowledge needed in designing and deploying a successful telephone system as we will also look ahead in new technologies used in the industry and emerging markets.

Types of Telephone Systems

The building telephone system can be divided into two;

  • The analog telephone system
  • The digital telephone system

The analog telephone system is also known as the conventional telephone system that is used in residential buildings while the digital telephone system on the other hand simply involves using an Electronic Private Automatic Branch eXchange (EPABX OR PBX OR PABX). The digital telephone system is mainly deployed in offices, companies, hotels, banks, and hospitals. 

Let’s explore the three component of a telephone system;

  • The distribution frame
  • The telephone outlet and jack
  • The distribution cable

The Telephone distribution frame

The Telephone distribution frame is a passive device where telephone cables terminate allowing arbitrary interconnections to be made. They can be divided into two; A-Main Distribution Frame (MDF) and Intermediate Distribution Frame (IDF).

Main Distribution Frame (MDF) is the main panelboard for telephone lines in the building. It is the frame where the entire telephone lines are terminated in the building.

Intermediate Distribution Frame (IDF) is the sub-distribution board for telephone lines in a large building. It is the frame that manages the telephone lines for a floor or zone.

The distribution frame exists in different capacities pairs as required.

The Telephone Outlet (Jack)

Telephone jack is the interface that connects telephone sets to the building telephone outlet. The telephone distribution line runs from the telephone outlet (jack) to the telephone boxes or distribution frame directly. It comprises of a cable of twisted pairs and modular jack with numbers of contact. The combination is termed RJ-11 (Registered Jack 11).

Another outlet that you will find when dealing with the telephone system is the RJ-45 telephone outlet. This outlet has additional wires (8 wires) to enable internet connection for making phone calls. They are used for VoIP telephones (voice over IP).

The outlets should be installed at a height of 350 mm from the surface of the floor and be of connectors distinct from other outlets.

The Distribution Cable

The ordinary twisted pair cable wire diameter of 0.6sqrmm is being used for the telephone system while Cat6 fiber optic cable is used in connecting the telephone lines to the router in a VoIP telephone system.

Each line must be isolated from the rest of the electrical connections and have separate conduit pipes while installing them to prevent attenuation.

Download a sample Telephone project Design

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