The original Bell Telephone system was required to provide 99.999% (or five nines of) relability. This level of reliablilty equals 5 minutes of downtime per year. In contrast to 97% reliability which is equivalent to 263 hours of downtime per year.
The original Bell Telephone system was required to provide 99.999% (or five nines of) relability. This level of reliablilty equals 5 minutes of downtime per year. In contrast to 97% reliability which is equivalent to 263 hours of downtime per year.