SP-1 switch: Difference between revisions
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m moved SP1 (telecommuncations) to SP1 (telecommunications): typo |
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Revision as of 10:29, 7 February 2006
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The SP-1 (Stored Program 1) was the name of a computerized telephone exchange (a so-called switching office) manufactured by Northern Electric (now Nortel Networks beginning in 1972) in Canada. It was introduced around 1967.
As indicated by its name (‘’’Stored Program’’’), the SP1 introduced computer control to the telephone switching market. A central computer controlled the operation of the switch. Switch behavior was determined by the operation of a computer program.
With its use of computer hardware and software control, the SP1 marked an evolutionary step in telephony design. It was an intermediate from linking the previous generation of electromechanical systems with the next generation of fully digital systems. Like the previous generation of systems, the SP1 was an analog switch that used a special form of mechanical relay (crossbar switch) to provide the voice connections. The voice signal remained in the analog domain throughout the switch with the switch providing a metallic path to connect the end points of a call together. However the SP1 replaced the previous generations use of relay-based computers (markers) with a modern (Harvard architecture with separate data and program memories) fully electronic computer design. The next generation of systems evolved from the SP1 design to replace the analog switch with a fully digital technology.
SP1 proved the feasibility of software-controlled systems for telephony. It set the stage for the introduction of fully digital systems with the development of the DMS (Digital Multiplex System) by Nortel in the 1970s.