customer's line outlet. If the line was idle then ringing voltage would be applied to the called line and ringing tone was sent to the calling line.
Another variant of the two-axis switch was the Stromberg-Carlson X-Y Switch which was quite common in telephone exchanges in the western USA. It was a flat mechanism, and the moving contacts moved both sidewise, as well as to and fro. It was quite reliable, and could be maintained by people with minimal training.
Applications of stepper switches
The sound of a step-by-step call reaching a busy circuit.
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As well as the decoding of pulses from telephones, 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 used in a series of Japanese cypher machines during World War 2: CORAL, JADE, PURPLE (the names were American). Some of the equipment used to break the Enigma machine code also used many such switches, which some observers called the "Machine Gun" for the loud noise.