Stepping Switch

Stepping switches change the direction of a magnetic flow to one of multiple channels, stepping through them incrementally. Which sounds incredibly boring until we realize they enabled the modern phone system and powered the decryption machines which morphed into the modern computer. Stepping switches were literally a step from the industrial revolution to the modern world.


Let’s step back. When you dial a phone number each digit zero’s in on the intended recipient. Take the theoretical number +1 212 345-6789. +1 indicated the US. The next set of numbers, 212, routes to the Washington, DC area. The next three numbers, 345, route your call to an exchange somewhere that used to be nearby your house. Finally, the last four digits find you.

Before stepping switches humans had to do manually. The +1 was implied (unless it wasn’t, in which case an overseas operator would reach the US). Dialing 212 is optional but, before stepping switches, if you wanted to dial long-distance an operator would have to plug your call into a long-distance line.

Finally, for the last part, an operator would always have to find you and plug the call in.

In case you’re wondering how this worked you would pick up the phone and tell the operator the number you wished to call. She (it was always a she) would then work with operators to get to the telephone you wished to reach.

If this sounds slow, clunky, annoying and expensive you’re right, it was. Therefore, Almon Stowger invented a device to do the work automatically. Rather than an operator routing the line, a series of stepping switches does the same work faster, cheaper, and more accurately.

Stepping switches were integral to the war effort. In Bletchley Park, the English code-breaking facility, they allowed the Allies to break Nazi encryption. Alan Turing, inventor of the modern computer, worked as a lead scientist.

Binary Theory

In 1935 theoretical mathematician Alan Turing proposed a machine that would use a series of on and off switches that could represent or compute anything.

Turing joined the war effort to build mechanical computers that decrypted Enigma messages. Eventually, he helped with electronic computers. His theories underpin all modern computers.

Subsequently, Turing envisaged reasonably sentient artificial intelligence, an idea that was ridiculous in his time. He ultimately developed the “Turing Test,” where a person could not tell whether they were communicating with a person or a computer. As of 2019, no computer program has yet to pass the Turing test.

Because of a conviction for homosexuality Turing was banned from computers on national security grounds. Subsequently, he committed suicide in 1954.

Electronic Cipher (Enigma)

Enigma is a cipher, a machine that implements an algorithm to encrypt and decrypt messages.

On Feb. 23, 1918, Scherbius applied for his first patent for what would become the most well-known cipher machine in history, the Enigma. Initially marketed for commercial purposes the German army modified a version for military encryption in 1926.

Nazis used Enigma extensively during WWII. They believed the encryption was unbreakable.

Decrypting Enigma messages required a new type of soldier, one more reliant on pencils and slide rules than rifles. These mathematicians and puzzle solvers were stations in the nondescript Bletchley Park.

Their work, led in large part by Alan Turing, both broke the Enigma encryption and eventually led to the innovation of the modern computer.

Scherbius died in an accident in 1929, long before WWII and the widespread use of his machine.

“The intelligence which has emanated from you before and during this campaign has been of priceless value to me. It has simplified my task as a commander enormously. It has saved thousands of British and American lives and, in no small way, contributed to the speed with which the enemy was routed and eventually forced to surrender.”

Letter from Gen. (later President) Eisenhower to the workers of Bletchley for breaking Enigma, Jul. 12, 1945