West Coast voice network infrastructure, 1942

"Late in 1940, the Bell System began one of the most remarkable plowing jobs of all time -- the burying of cables on a 1600-mile route from Omaha, Nebraska, to Sacramento, California. At these terminal points the cables will connect with cable systems already serving the East and Pacific West. There will thus be provided the first all-cable telephone route between the two coasts of the United States.

"The line consists of two cables buried, for almost their entire length, directly in the ground, without ducts or conduits. This is made possible by the use of cables designed for this purpose and protected against damage by gophers and other burrowing animals. ...

"As shown on the accompanying map, the cables will supplement four existing open-wire transcontinental telephone routes. Special equipment will make possible twelve talking channels for each two pairs of wires. One cable will contain the westbound channels; the other, the eastbound. Nearly 100 repeater stations will be used to strengthen the speech currents on their 1600-mile journey.

"Initially, the new cables will increase transcontinental facilities by about fifty per cent and ultimately will almost triple present coast-to-coast facilities."

The text says how many circuits (12) are carried by each pair of wires, but not how many pairs of wires are in each cable. But the opposite page has an illustration of a coax cable with the following caption:

Notable among Bell System developments of the past decade is the "coaxial" cable, a cross section of which is shown above. This can transmit 480 two-way telephone messages at the same time.