1940 – a full-scale relay calculator designed by Bell Labs engineer Dr. George Stibitz, becomes operational. The machine was first designed in February 1938, and construction began in April, 1939. Although the device was ready by October, 1939, it didn’t go into operation until this day.
The Complex Computer used 400-450 binary relays and initially could only run complex multiplication and division. The machine had to be modified to do addition and subtraction. In September, the device was connected to phone lines, sending information to a teletype unit.