By Steven Shepard, Contributing Columnist
By anyone’s estimation, 1891 was an eventful year. It saw the birth of a plethora of people who would go on to change the world: David Sarnoff, who would lead the invention of video. Earl Warren, who would sit on the US Supreme Court as its Chief Justice. Erwin Rommel, who would (albeit reluctantly) lead the Axis powers in North Africa during World War II. Fanny Brice, singing comedienne. Henry Miller, author. And Sergey Prokofiev, composer of extraordinary music.
1891 also saw a few deaths that would shake the world: Herman Melville, author of Billy Budd and Moby Dick. And Sherlock Holmes, whose character investigated his last case that year.
The year also saw its share of social and technological innovations. On March 21st, a Hatfield married a McCoy, ending a decades-long feud in West Virginia. Carnegie Hall opened on May 5th, with Tchaikovsky as the guest conductor.
Thomas Edison patented two technologies: the motion picture movie camera on August 24th, and the transmission of electrical signals for radio on December 29th. On July 7th the traveler’s check was patented, and on November 10th Granville T. Woods patented the electric railway.
But there was another invention that made its way into the patent files on March 10th of that year. Almon Strowger, undertaker, filed patent No. 447,918, which read as follows:
“In a system of electrical exchange, the combination, with an insulating curved surface, a system of wires having their ends extending to and through said surface to the concave surface thereof, and a rotary and longitudinally-moveable rod located at the axis of curvature, of a contact-needle fastened to the rod, levers for moving the rod longitudinally, levers for rotating the rod, magnets for vibrating the lever, and means for energizing the magnets at pleasure, substantially as set forth….”
Let me explain. Strowger, as we’ve noted, was an undertaker in Missouri. He noted at some point that his business was declining, not because the death rate in Missouri had dropped but because his competitor was married to – wait for it – the town’s telephone switchboard operator.
So when a call came to her from a distraught resident looking for the undertaker, the call naturally went to her husband, denying the customer the option to choose. Unless they specifically requested Strowger, the call went to her husband. Strowger found out, and the rest is technological history.
Automatic Telephone Exchange Invention
Strowger started with a cardboard cylinder and stuck ten rows of ten straight pins each through it, pointing inward. He then placed a lead pencil in the center and attached a metal wiper to the pencil that was long enough to reach each pin. He knew that if he could have the wiper move up and down on the pencil and also have the pencil rotate, he could create a connection with any of the contacts (the pins) in any of the ten rows.
Strowger also calculated that if he could assign one of these devices to each subscriber in a telephone system, then any subscriber could theoretically connect to any other subscriber by simply telling the system what to do to make the proper electrical connections. And the best way to do that, he theorized, was by using electromagnets to cause things to move.
But how would the electromagnets be controlled? This was the magic of Strowger’s device. He determined that some kind of key or button at the customer’s home or office would be ideal. But of course, he would have to connect each button to a magnet, which means that he’d need one wire to actuate the vertically-stepping magnet; one to actuate the rotary-stepping magnet; one that would trigger the transmission of ringing voltage; one would release the connection at the end of the call; and a ground.
That’s five wires running between the subscriber and the central office’ luckily we moved beyond that rather quickly, reducing the number of wires from five to two.
At any rate, today, March 10th, is the 121st anniversary of the award of Strowger’s patent. I think it’s important to reflect on Strowger’s technological contribution, but it’s at least as important to recognize that his switch gave telephone customers choice — for the very first time.