A typical telephone-exchange switchboard, ca. 1943. When you count how many leads and cables and sockets there are, it’s no wonder people wanted short numbers so that you didn’t clutter everything up! The end of Alphanumeric Telephone Numbers.
My "Nana" was a "PBX" Operator connecting calls to phone lines to complete the calls. It made her deaf in one ear & swapped jobs there and started dipping candies at "Sailors Chocolate's" in Alameda. My Brother and Sisters and myself visited her at work & watch her dip & wrap chocolates. We always sampled a few ( a bunch) & take some home. Like "I Love Lucy" working on the line & chocolate's were falling off the end so she was stuffing her mouth and clothes full so she wouldn't get fired.