Telephonic communications – Call signal generating
Reexamination Certificate
2005-04-12
2005-04-12
Barnie, Rexford (Department: 2643)
Telephonic communications
Call signal generating
C379S252000
Reexamination Certificate
active
06879687
ABSTRACT:
An apparatus which produces a ringing signal for a telephone system, effectively suppressing impulse noises. A ringing voltage generator produces a ringing voltage. A ringing signal sending unit sends a ringing signal to the called telephone terminal over the subscriber line by outputting the ringing voltage intermittently. This ringing signal consists of ringing periods and silent periods which will appear alternately with a prescribed duty cycle. One of those silent periods is used by a data transfer unit used to transport data to the called terminal. A feed impedance setting unit provides a feed voltage with higher source impedance. A feed impedance selection unit selects a low-impedance feed voltage in the one of the silent periods during which a data transfer is performed, and selects a high-impedance feed voltage in the other silent periods during which no data transfer is scheduled.
REFERENCES:
patent: 4551581 (1985-11-01), Doughty
patent: 6115469 (2000-09-01), Dalal et al.
patent: 61-500089 (1986-01-01), None
patent: 62078941 (1987-04-01), None
patent: 362078941 (1987-04-01), None
patent: 03-088464 (1991-04-01), None
patent: 09-162975 (1997-06-01), None
Barnie Rexford
Fujitsu Limited
Jamal Alexander
Katten Muchin Zavis & Rosenman
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