Telephone system is the most commonly used system in the Offices and Plants as it is the main means of wired communication within the premises and also to the external world. Traditional Telephone System is Analogue type which is slowly being replaced by the IP version. There are also systems that are hybrid that is they support both Analogue & IP within one system. The main equipment is the PABX which is the heart of the system follow by the Telephone Handsets which comes in all varieties like analogue, digital & IP type, indoor, outdoor, weather-proof and ex-proof version and other important components in the system like MDF, IDF, and Cables etc.