I once had a dream to create a phreak box that would be widely known and included in lists of boxes. The closest I got was a malicious combination of two preexisting boxes.
This was long ago, please don't judge me for the maliciousness of this box, I was young and nieve. I post it now for edcationaland novelty purposes ONLY.
Use a beige box to dial a 900 number that charges you by the minute to listen to a recording or sit at a menu.
Then use a scarlet box to tie the line, connect the red and green ports with a piece of wire is all a scarlet box is. Do this while still conected to the 900 number with the beige box. After the scarlet box is in place, remove the beige box and the call will NOT disconect due to the scarlet box. The victim will continue to be billed untill the scarlet box is removed.
I don't know what good this is, but it just intrigued me that a scarlet box can keep a connection going without any phone on the line being off the hook, thats the reason I made this box. I've never used it in the way described above.(dialing a 900 #) and i hope no one does.