A method of generating a subscriber line ringing signal includes the step of applying a time-varying waveform W(t) to the tip line while maintaining the ring line at a pre-determined supply level for a duration T/2. The time-varying waveform is subsequently applied to the ring line while maintaining the tip line at the pre-determined supply level for the duration T/2. A subscriber line interface circuit apparatus includes a power supply providing a time-varying supply level, W(t). A signal processor controls a linefeed driver to alternately couple W(t) to one of the tip and ring lines while coupling an alternate supply level to the other of the tip and ring lines for a duration T/2. In various embodiments, the resulting differential ringing signal is trapezoidal or sinusoidal.