Modern Telecommunications Technologies
It is difficult to appreciate the tremendous technological change that has been occurring in telecommunications in recent years and the impact of this change on market structure without delving into the technology to some extent. In this chapter the telecommunications technologies employed in the recent past, the present, and those likely to be put into practice in the near future are described in layperson's terms. An understanding of the new and emerging technologies and their economic significance helps clarify the recent revolutionary developments in the telecommunications industry and highlights likely future trends.
The first communication system to use electricity to transmit messages was the telegraph, which still plays an important role in specialized, high-volume applications. The simplest telegraph system consists of a pair of stations, each with a telegraph key, connected by two wires. At the sending station, the operator momentarily depresses a key to connect a battery to the two wires, causing a pulse of current to flow. The momentary current flow in the wires is detected as it passes through an electromagnet at the receiving station. The electromagnet, a piece of soft iron surrounded by a coil of wire, rings a bell or sounds a tone or click. Communication occurs by using the key to send a pattern of short and long pulses of current to spell out letters and numerals. The code invented by Samuel Morse was in universal use for this purpose until the 1920s.
The classic telegraph system is very slow, prone to errors because different letters are represented by pulse patterns of different lengths, and requires human operators at each end. In later systems telegraph