Edison once worked for the railroad. Something happened that changed the course of his career. Edison saved the life of a station official’s child, who had fallen onto the tracks of an oncoming train. For his bravery, the boy’s father taught Edison how to use the telegraph. From 1862 to 1868, Edison worked as a roving telegrapher in the Midwest, the South, Canada, and New England. During this time, he began developing a telegraphic repeating instrument that made it possible to transmit message automatically. Edison moved to New York City. Within a year, he was able to open a workshop in Newark, New Jersey. He produced the Edison Universal Stock Printer, the automatic telegraph, the quadruple, as well as other printing telegraphs, while working out of Newark. Thomas Alva Edison died in West Orange, New Jersey on October 18, 1931. At the time of this death, he was experimenting on rubber from goldenrod. After his death, Edison became a folk hero of legendary status. His inventions had truly and profoundly affected the shaping of modern society.“ … as well as other printing telegraphs, while working out of Newark” ( paragraph 3)

What is the closest in meaning to the word 'while"?​