Yeah, I don't think cell phones do fast-busy. They just timeout dialing without a carrier driven noise (mine have usually made the boop-boop noise like when the other party hangs up). Of course, with a cell phone, you can never tell if it's the network is busy or the tower is out of range, or the tower is broken. With a landline, you can tell if the line is dead (totally disconnected), really broken (voltage on the line, but no dialtone), or just pretty overloaded (dial tone, but fast busy for all numbers). And, if you made a habit of calling very busy numbers (like Netzero dial-ups), you could learn the tricks to get better priority; dialing the first N-1 digits, waiting a few seconds, and then the final digit would get me a waiting modem way better than just auto-redial on busy.