Patent ID: 7181004

Claim:
A method of generating a subscriber line ringing signal for a subscriber line having first and second lines, comprising: a) applying a time-varying supply level W(t)=|f(t)−C|+C+D to the first line while applying an alternate source V ALT (t)=D to the second line when f(t)−C>0, wherein D is a supply level DC offset, wherein C is a folding line about which f(t) is folded, wherein C≠0; and b) applying the time-varying supply level to the second line while applying the alternate source to the second line when f(t)−C≦0, wherein a resulting ringing signal component of the first line is L 1 (t), wherein a resulting ringing signal component of the second line is L 2 (t), wherein the first and second lines form a differential ringing signal line pair providing the differential ringing signal ΔL(t)=L 1 (t)−L 2 (t)=f(t).