AT&T L-4 Transcontinental Cable

Across the county road from my parents farm, north of Waterville, KS, is the tower pictured above. It was apparently some sort of repeater or monitoring site along a transcontinental telephone cable installed in the 1960's or 1970's. The cable was removed in the early 1990's, perhaps since the cable had heavy lead shielding (environmental concerns) or perhaps since AT&T didn't wish to maintain the right-of-way.

Pictured above is a cross-section of cable (the L4 20-tube cable) similar to that removed. You can see around the outer edge a black plastic coating, and inside that thick lead shielding. The cable contained 20 coaxial cable "tubes" for carrying telephone signals, and many smaller wires for other purposes. See the cross-section diagram below.

When the cable was in service, AT&T would fly over the cable route weekly (if I remember correctly). The cable was evidently, even in the 1980's, a very important asset to AT&T, and they didn't want anybody accidently cutting their cable. At one time, we had a water line trenched across the road from the cable, several hundred feet away from it at the closest. One day the AT&T plane flew over, noticed the trenching going on, and soon there was an AT&T truck that pulled up to make sure that noone was going to dig near the cable.

At one time, the cable may have been quite important to national defense. The map above, copied from notes about the AT&T L-4 system at http://www.alleged.com/telephone/L4/, shows that the L-4 cable from Fairview, KS to Lamar, CO (which the Waterville tower was on) was one of only two transcontinental cables crossing the midwest. Since the Fairview switching center was connected to the Strategic Air Command at Offutt AFB, Nebraska, and the Lamar switching center was surely connected to NORAD at Cheyenne Mountain, Colorado, this cable was probably fairly important to not only AT&T but the US Department of Defense as well.

T1: 24 voice circuits, 1.544Mbps data rate. L-4: 20tubes x 3600 voice circuits/tube = 72000, but figures say 32400. ~ 2.08Gbps ?!?

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