Posted to FB Antique Telephones group as a reply to Kevin J. Fitzgerald
I helped some students in our computer lab, and one high school kid, I think his name was Robert, was totally into phones. He had written a Basic program that printed a list out, with the various exchanges in the 714 area code, and what type of exchange they were. He could tell me what type of equipment the CO had, etc., etc. He knew, just by listening to the call progression what it was.
I called him up one time, and put “dial tone” on the line, and he didn’t know that I had built two oscillators 350 and 440 Hz, that generated the dial tone. But he tried the touch tones, and when nothing happened, he figured out that I was making the dial tone. 😄