Key telephone systems (abbreviated as KTP, sometimes called a key station) are traditionally used by companies with fewer than 50 employees. It is a telephone system with multiple buttons and lights that indicate which lines are in use. When you want to place a call, you just press a button to directly select the telephone company’s central office phone lines. Key phone systems are usually found in small companies where few features are required. Analog, digital, and Internet-enabled versions of key phones are available.