Method for remote power fail detection and maintaining continuous operation for data and voice devices operating over local loops
First Claim
1. An improved system for maintaining voice communications in a voice and data communications system, said system comprising:
- first and second voice and data modem means disposed at a subscriber location and a central office location, respectively, wherein each of said respective voice and data modem means include voice and data input means and output means;
first and second transformer means for coupling the output means of said respective first and second modem means to telephone lines, said first and second transformer means each including a winding having a centertap terminal, the centertap terminal of said first transformer means being split and coupled to a sealing current source and the centertap terminal of said second transformer means being coupled to ground;
means for detecting a power failure at said subscriber location; and
,means for bypassing said first and second voice and data modem means and said first and second transformer means upon detecting power failure at said subscriber location.
2 Assignments
0 Petitions
Accused Products
Abstract
First and second ISDN modems are disposed at a subscriber location and telephone system central office and are arranged to operate in a normal mode, and in a bypass mode upon power failure at the subscriber location. The modems are coupled through the telephone lines via interface transformers having centertaps. The centertap at the subscriber location is split and coupled to a sealing current source and that at the central office is coupled to a sealing current detector and ground. Sealing current flows between the respective transformers during normal operation. A drop in sealing current due to subscriber power failure is sensed at the central office, causing local logic to bypass the central office interface transformer and to couple the central office voice switch directly to the telephone lines. Loop current detectors at the subscriber location and at the central office determine whether the subscriber location voice telephone device is on-hook. If power is restored when on-hook, the local logic recouples the output interface transformer to the telephone lines and the voice telephone device is recoupled to the modem. At the same time, the central office detects whether sealing current has been restored and whether the subscriber voice device is on-hook, and recouples its output interface transformer to the telephone lines and the voice switch to the input interface of the central office modem, resulting in restoration of normal operation.
124 Citations
10 Claims
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1. An improved system for maintaining voice communications in a voice and data communications system, said system comprising:
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first and second voice and data modem means disposed at a subscriber location and a central office location, respectively, wherein each of said respective voice and data modem means include voice and data input means and output means; first and second transformer means for coupling the output means of said respective first and second modem means to telephone lines, said first and second transformer means each including a winding having a centertap terminal, the centertap terminal of said first transformer means being split and coupled to a sealing current source and the centertap terminal of said second transformer means being coupled to ground; means for detecting a power failure at said subscriber location; and
,means for bypassing said first and second voice and data modem means and said first and second transformer means upon detecting power failure at said subscriber location. - View Dependent Claims (2, 3)
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4. An improved method for maintaining voice communications in a voice and data communications system, said method comprising:
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disposing first and second voice and data modem means at a subscriber location and a central office location, respectively; coupling said respective first and second modem means to telephone lines with first and second transformer means wherein each of said transformer means include a winding having a centertap terminal, said centertap terminal of said first transformer means being split; detecting a power failure at said subscriber location; and bypassing said first and second voice and data modem means and said first and second transformer means upon detecting power failure at said subscriber location. - View Dependent Claims (5, 6, 7, 8, 9)
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10. An improved system for maintaining voice communication in an ISDN modem system under power fail conditions, said system comprising:
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subscriber location ISDN modem means, said subscriber location ISDN modem means having an output interface comprising a transformer having a split center-tap terminal and sealing current source, a first input interface coupled to a voice telephone device with first selective coupling means and a second input interface coupled to a data terminal; means for coupling said subscriber location output interface to telephone lines with second selective coupling means; first detecting means for detecting whether said telephone device is on-hook; subscriber location logic means for actuating said first and second selective coupling means to de-couple said telephone means from said first input interface and to couple said telephone means to said telephone lines and to de-couple said output interface from said telephone lines when a subscriber location power failure occurs, said logic means including means for detecting the return of power to said subscriber location and for actuating said first and second coupling means to couple said telephone means to said first input interface and to couple said output interface to said telephone lines when power is detected and when said first detecting means indicates said telephone device is on-hook; telephone system central office ISDN modem means, said telephone system central office ISDN modem including an output interface means comprising a transformer having a centertap terminal coupled to a sealing current detector, a first input interface coupled to a voice switch with a third selective coupling means and a second input interface coupled to a data processing device; means for coupling said telephone system central office location output interface to telephone lines with fourth selective coupling means; second detecting means for detecting whether said telephone device is on-hook; and telephone system central office location logic means having an input coupled to said sealing current detector means, for actuating said third and fourth selective coupling means to de-couple said voice switch means from said first input interface of said telephone system central office ISDN modem and to couple said voice switch means to telephone lines and to de-couple said output interface from said telephone lines when a subscriber location power failure occurs as indicated by said sealing current detector means, said logic means including means for actuating said third and fourth coupling means to couple said voice switch means to said first input interface to said telephone system central office ISDN modem and to couple said output interface to said telephone lines when sealing current is detected and when said second detecting means indicates said telephone device is on-hook.
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Specification