Telephone system is an old technology and still has it’s importance in today’s world. A telephone system is need when you have more than 1 incoming telephone lines. It is common for businesses to have 2-4 lines, for larger business they may even have 10 or 30 incoming lines. The telephone system allow the communcation between staff within the company via “extensions”. Although you have 2 incoming phone lines, your company can have 5 phones or extensions. The restriction here is, at any one time, only 2 person is able to communicate with someone outside the office.