Tied Up Telephone Lines

Tied Up Telephone Lines
One day a of network phone links between several major plants became tied up. What was causing this phone link problem?
Mysteries of Science


In the 1970s the telephone network used mechanical switching and relays. This system was slower than today's modern fiber-optics network, but it was reliable.

Big companies used tie lines and other leased phone links to handle calls from one plant to another. Since long distance calling was quite expensive, the network linked all of its 8 locations across the US. One plant could link to another by dialing a 1 or 2-digit code.

One day no lines could be accessed but the phone company said that the network was fine. This had never happened before. The Buffalo, NY plant was the most active using all the lines to Hopewell, VA. The Baton Rouge, LA plant was using all of their lines from their plant to Buffalo NY.

The 8 tie lines seemed to be forming a path from the Buffalo site to Baton Rouge and back. What was causing this strange linkup between the company sites? 

Here's the rest of the story.

One of the chemists apparently became intrigued with the tie line network. He dialed the first plant code and got a dial tone. Then he dialed that factory's code for a tie line to another plant, and so on. The final link was back to the Buffalo site, but once the dial tone sounded, he dialed the extension of the phone next to him. When his lab mate answered, he offered the normal "Hello", but the delays from thousands of miles of phone wire and all the amplifiers, caused about a 2 second delay.

When everyone realized that the two parties, who sat 20 feet apart, were talking over 25,000 miles of phone lines, everyone in the lab had to give it a try. There was something mystical about talking over the equivalent distance of the earth's circumference. In no time, the entire network was busy. Maybe there is no clear lesson here; perhaps it's to connect odd phenomena with odd individuals.


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