I read Dan Wagner's article on the Pyrex "Knob Top" in the February 1990 issue of Crown Jewels of the Wire with great interest. What a lucky guy!

I've known of the Phoenixville testing station for some time, having run across the page (below) from the Bell Telephone Quarterly (April 1939) when I was in school. I even detoured through the area last July on my way back to Baltimore after visiting the National. Needless to say, I found (or noticed) no trace of the "abandoned open wire line!"

The various Bell System publications over the years are full of interesting short articles and photos of open wire line topics. Wish we could exam some of the glass in the first photo!

Various Type of Insulators Undergoing Field Tests at Phoenixville, Pa.
In the Foreground is an Experimental Co-axial Conductor Line

Transmission Studies

There are also certain field stations where transmission tests have been carried on for a number of years. Oldest of these is the test station near Phoenixville, Pa. Crosstalk tests were begun here in 1919 by adapting an eight-mile section of an abandoned open-wire line. The location has been in practically continuous use ever since, principally as a proving ground for methods of transposing open-wire lines for high frequencies. One of these investigations showed the importance of close spacing between the wires of an open-wire pair.

Co-Axial Conductors entering the test house at Phoenixville [Pennsylvania].
 Here were conducted the first test of this structure as a medium for long-distance transmission.