Clear that nobody asked:
Pre-call screening was a different world. I measured how long until the ring was dropped, during the day, when it was easy to get through.
123 seconds. I used two payphones and a stop watch to be able to "capture the ring" by dialing in (a lot of payphones buffer the digits and send them after the last one pressed, good for the method because the new dial in was faster) and hanging up the first line at the right time, before the last couple digits of the new dial out. Tada, you have it. Basically YOU WILL be the next caller, if you always have the ring. Back then it was fun, I used it for my friend Theo, who was the fiddler call the night of hurricane bonnie if I'm not mistaken.
When Art would clear a line, I'd start the stopwatch, time delay and 123 seconds, thats the window. So indeed as previously speculated it was a timing thing. Everyone else walked into a closed guarded door, busy signal. Sometimes I'd change the timing by hanging up before the full time, in case someone else had enough discernment to "work the clock."
And there we have it, straight from the guy whom Art said proved it.