In the first part of this series I touched on the evolution of (landline) telephone switching — which began with operators handling calls manually and which ultimately became the job of computers.

One of the last stages along the way was an electro-mechanical relay-logic marvel of unsurpassed engineering complexity, the #5 Crossbar Switch.

The last post introduced the switch fabric through which calls are routed. This post explores how that fabric is controlled and what happens when we pick up the phone, dial it, and are connected to the remote end.

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