SL1

SL-1 is a digital PBX (Public Branch eXchange, or private telephone switchboard) developed at Bell-Northern Research in the early 1970s and manufactured by Northern Telecom Limited (later known as Nortel Networks, now Nortel). SL stands for Stored Logic (by Northern Telecom).

* Exploratory development on the digital technology at Northern Telecom began in 1969, in common for the SL-1 (PBX) and the DMS (public switch) product lines"L'empire Invisible" by Jean-Guy Rens, History of telecommunications in Canada, 1956-Today] .
* R&D activities related to the SL-1 started from June 1973.
* It's capacity ranged originally from 100 to 7,600 lines
* It is the member of Northern Telecom's digital switches family. It was announced by Northern Telecom in December 1975 (the DMS will be announced in January 1976)
* It is the first fully digital PBX announced on the global market. In the early 1970s, most PBXs were either electromechanical (e.g. cross-bar) or based on an hybrid technology (e.g. switching matrix made from a two-dimensional array of contacts but control performed by an electronic logic). For this reason, the SL-1 enjoyed a great success on the enterprise market both in North-America and globally.
* However, it is not the first digital switch since the inauguration of a first "public" digital transit exchange was announced by the Centre national d'études des télécommunications (CNET) in France in the city of Perros Guirrec in January 1970.
* The SL-1 was gradually enhanced (peripheral hardware, packaging, etc.) and renamed Meridian-1 in the late 1980s. The Meridian-1 has evolved to support IP telephony and other next generation IP services.

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