Electric power conversion systems – Current conversion – With means to selectively provide d.c. of either polarity
Patent
1992-07-31
1995-07-25
Stephan, Steven L.
Electric power conversion systems
Current conversion
With means to selectively provide d.c. of either polarity
H02M 702
Patent
active
054368227
ABSTRACT:
A polarity reversing DC power inserter circuit for remotely located equipment such as interdiction apparatus or other signal control apparatus used in a cable or community antenna television (CATV) signal distribution system. A power transformer circuit receives a 117 volts AC power source at a subscriber's premise and converts it to a lower voltage positive and negative DC. A polarity reversing circuit comprising switching transistors and a 50% duty cycle multivibrator switches between the lower voltage DC at a frequency less than 10 Hz so as to avoid shock hazards associated with normal alternating current, while alternating sufficiently often to avoid electrolysis and corrosion problems associated with use of direct current (DC) powering. The reversing polarity DC power is then inserted into a cable drop to be provided uplink to the signal control apparatus. At the signal control apparatus, the polarity reversing DC is converted into DC by a power utilization circuit, and then utilized to power the signal control apparatus.
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Campbell, W. Sherwood, "Powering the Off-Premises Signal Control System", 1985 NCTA Technical Papers, pp. 72-73.
Nguyen Matthew V.
Scientific-Atlanta, Inc.
Stephan Steven L.
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