seen from United States
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seen from Yemen
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seen from United States
seen from United States
seen from United States
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Did Bell use digital switches for long distance in 1978?
The No. 4 Electronic Switching System (ESS) would have been in service as early as 1976, slowly replacing the No. 4 Crossbar (XB) systems that made up the AT&T long lines network. The 4ESS was a step forward from the 1ESS and 1A ESS which were sorta like computer controlled XB switches... sorta.
Why do you ask?
