Telecommunication System

Modern Telecommunication is founded on a series of key concepts that skilled progressive growth and refinement in a period of well over a century. In the 1940s the invention of semiconductor devices made it potential to produce solid-state units, that are smaller, more efficient, reliable and durable, and cheaper than thermionic tubes. From the mid-1960s, thermionic tubes had been then being changed with the transistor. Thermionic tubes still have some functions for certain high-frequency amplifiers.