Telecommunication systems are generally designed by telecommunication engineers which sprang from technological improvements in the telegraph industry in the late 19th century and the radio and the telephone industries in the early 20th century. Today, telecommunication is widespread and devices that assist the process, such as the television, radio and telephone, are common in many parts of the world. There are also many networks that connect these devices, including computer networks, public switched telephone network (PSTN),[5] radio networks, and television networks. Computer communication across the Internet is one of many examples of telecommunication. [6] Telecommunication plays a vital role in the part of world economy and the telecommunication industry's revenue has been placed at just under 3% of the gross world product.