Copying here an interesting comment on the video from user @melkiorwiseman -

Fun Fact: The first step-by-step switch and indeed the very first automatic telephone exchange was invented by Almon Strowger. Almon Strowger was an undertaker by trade. He became convinced that the manual telephone exchange operator, who was the daughter of the only other undertaker in town, was deliberately directing all calls for "the undertaker" to her father's practice instead of dividing them equally between the two as was standard practice at the time. Strowger decided that he needed to invent a way for telephone customers to dial the number themselves and used cut out pieces of paper to represent the electrical contacts so that he could work out how the equipment should work. If I remember correctly, Strowger was granted a patent for his automatic telephone exchange in 1929. Strowger's exchange required two extra wires from the exchange to each telephone to carry the dialling signals, but some clever lateral thinking allowed for using the same two wires for nearly all signalling as well as for speech.