It happens. If you're only using the one phone line, just strap tip and ring to the yellow/slate leads going to the phone. Be sure to disconnect the jumpers connecting them to CA. Doubtful the cell to pots converter will have enough oomph to ring that old bell, but who knows.
I have some small ringing generators that convert 12 or 24 volts to 70v at 20hz. I wouldn't try to ring 4 phones with one, but it might ring one or two. I'll see if I can find one online....
