Stepping switch Guide, Meaning , Facts, Information and Description
In electrical controls, a stepping switch (also called a uniselector or Strowger switch) is an electromechanical device used, most prominently, in early automatic telephone exchanges to route calls. A basic stepping switch would have (usually) one stepping contact, one input contact and some number of outputs. Each time an electric pulse was received at the stepping contact, an electromagnet drove an internal rotary contact (called the wiper) to advance one position, and connect the input contact to the next output. Some stepping switches would be reset back to the "home" position as soon as they reached the last position, while others had a separate "reset" coil.Slightly more complicated was the two axis stepping switch which had two stepping coils, one to rotate the wiper and one to raise it up to successive banks of contacts. These were commonly used in telephone switching with ten banks of ten contacts.
Stepping switches could be used for a variety of purposes, depending on how they were wired. By connecting several in series with the highest output of one going to the stepping contact of the next, a counter could be constructed. Or by feeding the stepping contact with an endless pulse train via a relay, and controlling the relay from the switch's own output, it can be made to automatically hunt for the first unpowered line (or powered, depending on whether the relay is normally open or normally closed). They could also be used as a demultiplexer, so that two input lines could control a number of output devices. One input line steps the switch until the correct device is selected, and the other then powers that device. Many other applications are possible.
Such switches were also used in a series of Japanese cypher machines during World War 2: Red, Coral, Jade, PURPLE. (The names are those used US cryptographers and have nothing to do with any aspect of the cyphers — they are the colors of binders used to hold information about the cyphers as they were worked on.)
Stepping switches were invented by Almon Strowger in 1888.
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