[julie_m]

Yes, a "traditional" transformer with copper wire and a laminated steel core is what I meant.

Though if you have a low power switched-mode PSU that will work down to about 90V on the input and puts out enough to ring the bell clearly, you might try it anyway just for a laugh and carry-on.

I wouldn't expect it to work very well if it works at all, because the ringing current comes in short bursts and the SMPSU might not have time to start up properly before the end of the ringing pulse. The telephone ringing voltage being at the very bottom end of the power supply's working range isn't going to help matters, either. (But this would be a good thing for a traditional steel core, since the frequency is only 25Hz; this means that a half-cycle lasts twice as long as on the mains, so you'd end up trying to put twice the amount of flux through the core unless you reduced the voltage.)

But, who knows? If you can find a switched-mode phone charger that will start up from the telephone ringing voltage, deliver enough power to sound the bell and not consume so much energy that there isn't enough left to ring the other phones on the line, it would almost be a shame not to use such a crazy solution!