Stored Program Control exchange

In the modern time almost all the exchanges are controlled by computers through programs stored in the memory of the system. Such exchanges are called as Stored Program Control exchanges (SPC).Early exchanges such as Strowger, Panel, Rotary, and Crossbar were electro mechanical and had no software control. SPC was introduced  during 1960s on a small scale and was called as  Electronic Switching Systems. As SPC exchanges evolved, reliability and versatility increased. In the 1980s SPC completely took over the industry.