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Stored Program Control exchange
From Wikipedia, the free encyclopedia
Stored Program Control exchange (SPC) is the technical name used for telephone exchanges controlled by a computer program stored in the memory of the system. Early exchanges such as Strowger, Panel, Rotary, and Crossbar were electro mechanical and had no software control. SPC was introduced on a small scale in so called Electronic switching systems in the 1960s (the 101ESS PBX was a minor Bell System example) and on a large scale (1ESS switch was the major Bell System example) in the 1970s. SPC allowed more sophisticated Calling features. As SPC exchanges evolved, reliability and versatility increased. In the 1980s SPC completely took over the industry, hence the term lost all except historical interest.
