After identifying the prefixes by geographical location, it didn't take me long to determine that some actually went to phone exchanges operated by other phone companies. My scanning efforts came up with an amazing amount of numbers that behaved very strangely, by answering with a tone.

I found a number that actually delivered a dial tone, and one could dial other numbers through the tone. Later, I learned that these numbers were "demonstration" numbers, designed to demonstrate touch tone service in areas that didn't have them.

Our area did not have touch tone services until 3 years later. I also had a 2nd phone line, tied the lines together to see what happens when I dial out on both phone lines at once. Normally, one would be busy, and the other one would get through and rang.

Sometimes, they would jam, and I would hear a loud pop, and if I stayed on the line long enough, other callers would connect and we could talk. Then if other people called in, they also would connect.

Sometimes, when calling radio stations, I could hear people talking between the busy signal, and sometimes the busy signal was so weak that it was almost drowned out. It turns out that phone freaks use them to talk in large groups.

Knowing that there were certain restrictions that prefixes had during those times, I was able to eliminate a lot of unnessisary scanning.

Once I discovered the new frontiers that blue boxes afforded me, I was able to explore a whole new relm of numbers. These numbers were inter-city dial codes that operators from one city would use to reach operators in another. These were called routing codes, which are no longer used, but during the times I was experimenting, I was able to find out all sorts of internal numbers.