The New Yorker keeps an archive of old articles on line. One I found particularly interesting was called Invention Factory, from the November
28, 1931 issue. The Reporter at Large, Malcolm Ross, visited the main Bell Labs building in New York City. The Labs was working on many technologies at the time, including better magnets, vacuum tubes, transatlantic radiotelephony, movie audio, and of course the telephone network itself. I hope it's okay to post this full paragraph, which I particularly enjoyed, describing what I suspect was a predecessor of the crossbar tandem:Most research, in fact, is endless patience geared to an objective. For thirty years hundreds of workers have been at the job of perfecting an automatic switchboard. They have an approx- imation of perfection now in the person of a robot they call suburban tandem. If it isn't a person, it acts like one. Operator dials an out-of-town number for you. Suburban tandem - in appearance surpassing Rube Goldberg's worst nightmare - stores up the dial pulses and decides whether the terminus is manual or automatic. If manual, it selects a suitable trunk line, flashes the operator on the other end, and, by means of a film voice-record stretched on a revolving drum, announces to her in human tones that New York wants Summit 0001. When something goes wrong with suburban tandem, it rings a bell for the repairman, and spends the waiting minutes in typing out a diagnosis to show him when and where its indigestion began. Suburban tandem, said our guide, is the smartest piece of remote control of our times.