Telephonic communications – Call signal generating
Reexamination Certificate
2005-07-19
2005-07-19
Kuntz, Curtis (Department: 2643)
Telephonic communications
Call signal generating
C379S382000, C379S383000, C379S384000
Reexamination Certificate
active
06920220
ABSTRACT:
A circuit for closing a relay when an active AC voltage connected to one of the contacts of the relay is approximately zero volts includes a monitoring circuit that monitors the active AC voltage and outputs a phase-shifted voltage that crosses zero volts at predetermined times before the active AC voltage traverses zero volts. A pulse generating circuit initiates a pulse when the phase-shifted voltage enters a predefined voltage region and terminates the pulse when the voltage exits that region. An input signal is strobed onto the control input of the relay by the pulse so that the relay changes state coincident with the zero crossing of the active AC voltage.
REFERENCES:
patent: 4396805 (1983-08-01), Wagner
patent: 4631361 (1986-12-01), Miller
patent: 5185738 (1993-02-01), Kelly
patent: 5406623 (1995-04-01), Rovik
patent: 5636274 (1997-06-01), Youngblood
patent: 6115469 (2000-09-01), Dalal et al.
Brady W. James
Kuntz Curtis
Pham Tuan
Swayze, Jr. W. Daniel
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