When my friends tell me they're getting rid of their home phones - called a landline - and moving only to their mobile phones, I look them in the eye and say sternly "Remember the five nines!"
I'm not referring to any kind of numerology, but am alluding instead to the holy grail of reliability used by all engineers: The five nines refer to the numbers in ninety-nine point nine nine nine percent. [99.999%] The landline telephone network meets this standard: It operates 99.999% of the time. This translates into only five minutes of downtime in a year's operation. Contrast this to the 98% reliability of the cell phone network: That 98% sounds like a lot, but it means that for 10,500 minutes of every year a cell phone won't connect!
I know that it seems a brand, spanking new technology like cell phones should beat the heck out of a 19th century technology like landline phones. Yet those 19th century roots are the source of reliability.
For example, ever notice that in a blackout your phone stays on? Since the telephone system rose before a comprehensive power grid covered the country, the telephone company developed their own batteries that power your phone from the central switching station. In contrast cell phone towers depend on the power grid: No power to the tower, no service to the cell phone.
Through 100 years of slow and steady growth the telephone system has developed extremely reliable switches, even entering the digital age. Yet, again, a major source of reliability is a 19th century one: Human intervention. Yes, people still monitor the network's operation. In fact, many telephone outages are ended when a human sees something wrong and simply throws a switch.
Yet Landlines are disappearing. In the coming year some 19 million fewer people will drop their home phone lines. A new Federal Law allows cell customers to keep their number when they change wireless providers. This has enticed millions to "cut the cord" and rely only on cell phones. Will the cell phone network become as reliable as the landline network? Perhaps not.
You see right now the FCC and the Homeland Security Administration disagree about whether to make cell network outages public. The FCC says "yes," crediting the public reports of the landline companies with dramatically improving network quality. Homeland Security says "no", outage reports would be a blueprint for terrorists who want to disrupt the U.S. They would provide a road map for targeting network stress points and vulnerabilities.
Perhaps. But if we all just keep our 19th century phones, we could defend our 21st century communications from terroirst attacks!
Copyright 2004 William S. Hammack Enterprises