Note: Records for this film date it to 1955, but it documents events which took place in 1951.
This film chronicles the evolution of the coast-to-coast American telephone network, from the first linking of California to New York in 1915, to the microwave relay system inaugurated in 1951.
The technology that made this possible came out of the research done during WWII on radar systems, and the growth of the network following the war necessitated some rapid technological development to keep up with demand. The system used here was the TD2, which was the third generation of microwave relay technology. This system cost only 40 million dollars to deploy (358 million in today's dollars), serviced approximately 40 million telephones nationwide, and used 107 microwave relay towers.
The directional beams on the towers rapidly bounced the call signals across the country. This system was the backbone of long-distance service for almost the next three decades, when it was rendered obsolete by fiber optic cables. The microwave transmission technology continued to develop at Bell Labs, however, and became the basis for the cellular network and different types of localized cellular transmitters and receivers.
Footage courtesy of AT&T Archives and History Center, Warren, NJ