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US 4,903,292 AGranted
System for transmitting low frequency tones through a digital loop carrier system
AssigneeReliance Comm/Tec Corporation
InventorPhilip L. Dillon
Life of this patent
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AssigneeReliance Comm/Tec Corporation
InventorPhilip L. Dillon
Estimating the term…
A system for use in a digital loop carrier (DLC) which allows low frequency (sub-audible) tones such as those used with alarm systems to be transmitted from one end of the DLC to the other end even though the DLC has been designed to reject signasl below 200 Hz. The system may be added to an already installed DLC or included with the DLC prior to installation. At the end of the DLC from which the low tone is to be transmitted, the system controls the amplitude of the tone so that it can be encoded for transmission within a predetermined window. The DLC allows such low frequencies to be transmitted through the window while still rejecting 60 Hz signals (and its lower order harmonics). The controlled low tone and the voice signals are combined for transmission to the other end. At the other end, the decoded low tone is amplified by the system and then recombined with the decoded voice signals for use therein.
A digital loop carrier system comprising:
A system for transmitting a low frequency tone over a digital loop carrier system said carrier system having first and second ends, said first end including means having an input at which a first analog signal which includes said low frequency tone appears for passing only that part of said first analog signal which is in a predetermined frequency band above said tone frequency, said first end also including means for encoding said passed part of said first analog signal and an amplitude controlled tone into a digital signal for transmission to said second end, said second end including means for decoding said first end transmitted digital signal into a second analog signal which includes said tone, said tone transmitting system comprising:
A low frequency tone transmitting system for connection to a digital loop carrier system, said carrier system having first and second ends, said first end including means having an input at which a first analog signal which includes said low frequency tone appears for passing only that part of said first analog signal which is in a predetermined frequency band above said tone frequency, said first end also including means for encoding said passed part of said first analog signal and an amplitude controlled tone into a digital signal for transmission to said second end, said second end including means for decoding said first end transmitted digital signal into a second analog signal which includes said tone, said tone transmitting system comprising:
Dependencies are inferred from the claim text.