This chapter analyses the telecommunication systems, which are bilateral or reciprocal, that is, one-to-one, from person to person, position to position, or some combination of person and position. With the exception of postal systems, telecommunications systems have for the most part been a twentieth-century development. The telegraph and telephone emerged during the nineteenth century, but telecommunication between private citizens via electronic media did not become commonplace until the twentieth century. Telephones, two-way radios, intercom systems, and telematics and informatics have largely supplanted messengers as the primary means of transmitting information within and between complex social structures. Space-binding technologies are used to transmit information from location to location. The cellular telephone breaks the link of telecommunication nodes with specific places and refocuses telecommunication to individuals, wherever they happen to be located at a given moment. Today's cellular mobile phone is a voice communication device, but also a text messenger, video and still camera, calculator, day planner, and address book.