Below are goodies that could not be included in the book due to space constraints. Enjoy.
As explained in Exploding The Phone, loop arounds were telephone company test numbers that allowed two people to talk to each other, anonymously. One person would call one of the pair of loop numbers, another person would call the other, and the two people would be connected together. In some cases the loops didn't "supe" so the calls were free.
Collecting and trading loop around numbers was a popular pastime among phone phreaks, and many compiled lists of loop numbers. Here are two different collections of loop around numbers from two different phreaks from the 1970s:
Click on the images for pdfs.
Author interviews with Fred Belton and Alan Rubinstein, 2012.