Direct drive for a subscriber line differential ringing signal

Details Direct drive for a subscriber line differential ringing signal Direct drive for a subscriber line differential ringing signal

2007-02-20

2007-02-20

Tsang, Fan (Department: 2614)

Telephonic communications

Call signal generating

C379S031000, C379S077000, C379S088240, C379S361000

Reexamination Certificate

active

10664596

ABSTRACT:
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.

REFERENCES:
patent: 6735302 (2004-05-01), Caine et al.
patent: 2004/0174992 (2004-09-01), Apfel
Legerity, Inc., 2002, “VOICECHIP Le9502” Legerity, Inc. , 2002, Austin, Texas; www.legerity.com.

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